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An ebook is an electronic (or digital) version of a book. The term is used ambiguously to refer to either an individual work in a digital format, or a hardware device used to read books in digital format. Some users deprecate the second meaning in favour of the more precise "ebook device."

Though e-texts are available as digitally encoded books and the term is often used synonymously with the term ebook, that usage is deprecated. The term e-text is used for the more limited case of data in ASCII text format, while the more general e-book can be in a specialized (and, at times, proprietary) file format. An exception to this rule is the academic e-text, which commonly includes components such as facsimile images, apparatus criticus, and scholarly commentary on the work from one or more editors specially qualified to edit the author or work in question.

An ebook is commonly bundled by a publisher for distribution (as an ebook, an ezine, or a internet newspaper), whereas e-text is distributed in ASCII (or plain text), or in the case of academic works, in the form of discrete media such as compact discs. Metadata relating to the text are sometimes included with etext (though it appears more frequently with ebooks). Metadata commonly include details about author, title, publisher, and copyright date; less common are details regarding language, genre, relevant copyright conventions, etc.



The ebook community has many options when it comes to choosing a format for production. While the average end user might arguably simply want to read books, every format has its exponents and champions, and debates over "which format is best" can become intense. For the average end user to read a book, every format has its advantages and disadvantages. Formats available include, but are by no means limited to:

Plain text

Published as an ASCII text (or .txt), an e-text in the proper (strict) sense.

Computer-encoded text that consists only of human-readable characters from a given standard, with no other formatting or structural information. Plain text interchange is commonly used between computer systems that do not share higher-level protocols. ISO 8859 is a group of related ISO standards for 8-bit character encodings for use by computers. These standards are based on ASCII, the most widely used 7-bit character encoding.

Image files

An ebook can be distributed as a sequence of images, one for each page. In this way, any image format can be used as an ebook format. This method of distribution produces files very much larger than all others, and also has the disadvantage that the user cannot select text, nor can the ebook be read by a screen reader. Distribution as images is most suitable for comic books, books about art, or other very visual works.

Rich Text Format

Published as an .rtf

A standard formalized by Microsoft Corporation for specifying formatting of documents. RTF files are actually ASCII files with special commands to indicate formatting information, such as fonts and margins.

Standard Generalized Markup Language

Commonly known as SGML

Standardized metalanguage for the description of markup languages; a set of rules for using whatever markup vocabulary is adopted. This includes the TEI standard.

eXtensible Markup Language

Published as an .xml

A subset of SGML constituting a particular text markup metalanguage for defining markup languages for the interchange of structured data. The Unicode Standard is the reference character set for XML content. XML is a trademark of the World Wide Web Consortium.

Hypertext Markup Language

Published as an .html

The formatting language used for creating hypertext documents on the World Wide Web and controlling how Web pages appear.

Cascading Style Sheets Commonly known as .css

Some ebooks use this extension from standard HTML that allow designers to control multiple web page styles from a single file. Used to predefine page elements such as font size, color, and style; image placement; and background images, and have the same style applied to a series of web pages.


The TeX format is a popular academic format. TeX is a typesetting system written by Donald Knuth, especially for technical writing applications in the communities of mathematics, science, and computer science. TeX can typeset complex mathematical formulas, but is now also being used for many other typesetting tasks especially in template packages. LaTeX is a TeX document preparation system. LaTeX offers programmable features and facilities for automating aspects of typesetting and desktop publishing, especially numbering and cross-referencing, tables and figures, page layout, bibliographies. LaTeX was originally written in 1984 by Leslie Lamport and has become a leading method for using TeX; few people write in plain TeX any more. (current version: 2ε)


Published as an .ps

PostScript is a page description language used primarily in the electronic and desktop publishing areas for describing the contents of a printed page in a higher level than the actual output bitmap.

Portable Document Format

Published as an .pdf

A file format created by Adobe Systems, initially to provide a standard form for storing and editing printed publishable documents. Because documents in .pdf format can easily be seen and printed by users on a variety of computer and platform types, they are very common on the World Wide Web.

PDF files are created mainly using Adobe Acrobat, but Acrobat Capture and other Adobe products also support their creation. Acrobat Reader (now simply called Adobe Reader) is used to view PDF files. PDF files typically contain product manuals, brochures, magazine articles, or flyers as they can embed fonts, images, and other documents. A PDF file contains one or more page images, each of which you can zoom in on or out from. Acrobat PDF include interactive elements such as buttons for forms entry and for triggering sound and Quicktime or AVI movies. Acrobat PDF files are optimized for the Web by rendering text before graphic images and hypertext links. Adobe's PDF-like eBook format is incorporated into their reader.


Published as .djvu

DjVu is a file format that has been long in obscurity (in other words, since 1996), but that is starting to surface now that free tools to manipulate the files are available.

DjVu is a format that particularly excels in storing scanned images. There are even advanced compressors especially specializing in low-color images, such as text documents. Individual files may contain single pages, or they can be collections of multiple pages.

The images are divided in separate layers (such as multi-color, low-resolution, lossily-compressed background layer, and few-colors, high-resolution, tightly-compressed foreground layer), each compressed in best applicable method. The files are also designed to decompress very fast, even faster than vector-based formats.

The advantage of DjVu is that it is possible to take a high-resolution scan (300-400 DPI), good enough for both on-screen and printing, and store it very efficiently. Several dozens of 300 DPI black-and-white scans can be stored in less than a megabyte.


Published as an .lit

The MS reader uses patented ClearType® display technology. Navigation works with a keyboard, mouse, stylus, or through electronic bookmarks. The Catalogue Library records reader books in a personalized "home page". A user can add annotations and notes to any page, create large-print eBooks with a single command, or create free-form drawings in the reader pages. A built-in dictionary allows the user to look up words.

eReader (formerly Palm Digital Media)

Published as a .pdb

eReader is a program for viewing Palm Digital Media electronic books. Versions are available for PalmOS, PocketPC, Symbian OS, Windows, and Macintosh. The reader shows text one page at a time as paper books do. eReader supports embedded hyperlinks and images. Most eReader formatted books are encrypted, with the key being the purchaser's full name and credit card number.


Published as an .prc

The Mobipocket Reader has a home page library. Readers can add blank pages in any part of a book and add free-hand drawings. Annotations — highlights, bookmarks, notes, and drawings — can be applied, organized, and recalled from a single location. Mobipocket Reader has electronic bookmarks, appearing in the page margins. Dictionaries allow users to look up definitions through a built-in Lookup function.

The reader has a full screen mode for the reading experience and has Microsoft ClearType® support. On Palm OS, readers can use sub-pixel rendering with the MobiType® font. Mobipocket Reader is the only eBook Reader running on nearly all PDA types (Palm OS, Pocket PC and Windows CE, Tablet PC, Casio BE-300, Psion, Symbian OS Smartphones, Franklin eBookMan) and PCs.

The Mobipocket eBook format based on the Open eBook standard using XHTML can include JavaScript and frames for a dynamic display, which makes Mobipocket the best solution for professional content such as medical reference eBooks and dictionaries. It also supports native SQL queries to be used with embedded databases.

The Mobipocket encryption system is not a password based system. Its DRM relies on the PDA hardware serial number.

Mobipocket also provides a free eNews service. A reader can subscribe to notable periodicals, or create custom channels. Software on the PC updates the subscriptions and sends them automatically to the PDA.


Published as an .exe

ExeBook is a compiler that produces an ebook file that, when executed, produces a simulated book onscreen, complete with page texture. The etext is encrypted as graphic images so that automatic text copying is very difficult. The fear of exe files picking up viruses, however, is hampering its acceptance.


Published as an .exe and .dnl

DesktopAuthor is an electronic publishing suite that allows creation of digital web books with virtual turning pages. Digital web books of any epublication type can be written in this format, including ebrochures, ebooks, digital photo albums, ecards, digital diaries, online resumes, quizzes, exams, tests, forms and surveys. DesktopAuthor packages the ebook into a ".dnl" or ".exe" book. Each can be a single, plain stand-alone executable file which does not require any other programs to view it. DNL files can be viewed inside a web browser or stand-alone via the DNL Reader.

Comparison with printed books

Ebook advantages

  • Text can be searched, except when represented in the form of images.
  • Take up little space.
    • Hundreds (or thousands) may be carried together on one device.
    • Approximately 500 average ebooks can be stored on one CD (equivalent to a roomful of print books)
  • Ebooks may be read in low light or even total darkness, with a back-lit device.
  • Type size and type face may be adjusted. However, enlarging e.g. a PDF document magnifies the text but preserves the original layout and spacing; a practical limit on zooming follows from the requirement to keep a text column within the width of the screen (otherwise horizontal scrolling would be needed during and after reading each line, which would be very cumbersome). However, tagged PDFs can be reflowed in Acrobat 6 and 7, eliminating the horizontal-scrolling problem in zoomed PDFs. For more on zooming in, see Electronic maps.
  • Can be used with text-to-speech software.
  • Readily reformatted for independent platforms.
  • Instantly copied
    • When a backup is kept in a remote place, cannot be lost by fire, etc.
    • Once distributed, elimination is hard to impossible.
  • Distributed at low cost.
  • Simultaneously share book (if networked).
  • Errors may be easily corrected with downloadable lists of errata or simply with corrected text. (This can also be an advantage for printed books, in different circumstances.)
  • At the moment, ebooks are commonly published by independent publishing houses, which can mean greater editorial and authorial freedom and more room for experimentation.
  • An inexpensive format for works that require color.
  • An excellent choice of format for works that benefit from search and cross-reference capabilities, such as dictionaries, reference works, certain kinds of textbooks.

Print book advantages

  • Less eye strain over extended reading time
  • If small, very portable.
  • Usable in adverse environmental conditions.
  • Robust and durable.
  • Readable when severely damaged.
  • Requires no power source, and no alternative reading device like a PC or a palmtop.
  • Errors are "forever"; this unchangeability sometimes adds to its value.
  • Has more value as "collector's items," e.g., first editions
  • At the moment, print books are primarily published by established houses including numerous international conglomerates, which can result in greater funds available for promotion of a title.

Ebook disadvantages

  • From the user's point of view: Can be incompatible with new or replacement hardware or software
  • Require care in handling and storage of the files, to avoid damage or loss
  • From the publisher/author's point of view: Can in some cases be hacked, or disseminated without approval from the author or publisher (some formats are more susceptible to this than others)
  • Not normally a good format choice for works that have extensive and/or large illustrations, such as works in art history, photography, large maps, etc.

Print book disadvantages

  • From the user's point of view: Can be priced in a way that inhibits availability
  • From the user's and author's point of view: Can be put out of print and made unavailable to readers
  • From the author's point of view: Can be difficult to get a publisher to amend errata
  • Can be an awkward format for reference works or works that have many internal crossreferences.
  • An expensive format for works that require color, since color printing commonly requires several passes of paper through the press (one pass per color).


Of these, the main contenders appear to be HTML, ASCII, PDF, and recently XML. The various distribution formats, HTML, ASCII, PDF and XML are widespread, but are usually used in low-level, non-critical, and non-commercial formats. Microsoft Reader 2.0, Mobipocket Reader, Palm eReader and Adobe Acrobat Reader are in widespread use. ExeBook and DesktopAuthor are making some inroads on the PC, but are not nearly as widespread. TeX is usually considered too complex for general use, but its advanced formatting abilities are very important in technical writing. The distribution choice of format, to some extent, depends on the aims of the publisher of the ebook.


Currently available purpose-built ebook reading devices include the Cybook (from Bookeen, available in English and French versions from their web shop), the Librie (from Sony, available in Japan only) and the Hiebook (from Hiebook, available in Korea only). The advantage of these devices lies in their large display and design providing the best immersive reading conditions. Formerly available devices include the Rocket eBook (Nuvomedia), the Softbook (Softbook) and the eBookman (Franklin).

Many Personal digital assistant (PDA) devices, such as PocketPC or Palm, allow to read ebooks since their inception. As the PDA market represent millions of customers worldwide, PDAs remain a popular sector for reading ebooks.


Ebook projects generally fall into two camps (ed. though the creators and publishers are often unclear as to which camp they belong):

New Creation: Publishing solely online editions, where exact reproduction of printed matter is unimportant.
Reproduction: Accurate reproduction of existing paper editions, where it becomes important to preserve features of the original, such as pagination.

The Internet Public Library, the first public library of and for the Internet community, is an experiment trying to discover and promote the most effective roles and contributions of librarians to the Internet and vice versa.

There are many reproduction projects on the Internet. Project Gutenberg is a project to create an archive of ebooks, having started in 1971. Project Gutenberg may claim to be the earliest project to create an archive of ebooks. Many other projects have followed, mostly based on public domain texts (which themselves are often derived from Project Gutenberg). Some of these include:

  • John Mark Ockerbloom's Online Books Page, hosted by the library of the University of Pennsylvania.
  • The Oxford Text Archive, hosted by the Arts and Humanities Data Service.
  • Making of America (MoA), a digital library of primary sources in American social history from the antebellum period through reconstruction.

While no single directory of available ebooks exists, see List of digital library projects for links to articles and external sites for many digital library projects.

E-publishing ventures

Publishers are producing ebooks and now in the 21st century some publishers are expanding the market. For commercial publication, some publishers believe that digital rights management is all important, and tends to override other considerations in the choice of format. Many publishers are reluctant to produce ebooks over fears of piracy and it wasn't until the 21st century that many publishers considered it a worthwhile forum. Recent history has seen players such as Microsoft, Adobe and Mobipocket enter the market with purpose built software which addresses the right management needs of commercial publishers.

Alternatively, other publishers have found that making ebooks available without digital rights management can expand the market penetration of their paper books. Notable in this movement is Baen Books and National Academies Press. Baen and NAP make all their new books available in non-DRM formats, and have made a profit from its e-publishing, and the Baen Free Library is an experiment with making the full text of books available free for download. To date, Baen authors claim that this has increased their sales. Similarly National Academies Press publishes all of its 2,500 books both in free online editions and in priced printed editions and claims that the free editions stimulate sales of the priced editions. (See National Academies Press info site (http://www.nap.edu/info/site.html) for their rationale.) Additionally MIT Press claims that freely downloadable copies of their textbooks have increased paper sales.

The 1988 ebook of William Gibson's Mona Lisa Overdrive is a classic in the world of epublishing, and, on March 14, 2000, Stephen King's Riding the Bullet was downloaded by half a million people (only the first part of the book was free, and King gave up when he couldn't get enough people to pay for the remaining parts). The popular ebookstore and e-tailer, Amazon.com, sells ebooks in the two most popular formats, Microsoft's Reader format and Adobe's eBook format. Fictionwise.com is also a popular online ebook store that sells ebooks in a variety of formats, including Mobipocket format. Citing profitability concerns, Barnes and Noble stopped selling ebooks in 2003. Mobipocket was acquired by Amazon.com in April 2005.

The lack of legitimate ebooks has led to rapid growth of the number of unlicensed ebooks being produced, a growth which still continues - most significantly in the genres of science fiction and fantasy. This had resulted in the number of unlicensed ebooks to outweigh the licensed ebooks by several orders of magnitude.

Recent attempts to revive ebooks include ExeBook and DesktopAuthor, ebook compilers that produce a simulated book onscreen. These formats are not nearly as popular as others (notably PDF, PDB, MS Reader and Mobipocket) due to their PC-only nature not being available on other platforms (such as Macintosh, Linux, and Palm), fear of EXE files picking up viruses, and a general reluctance by publishers to move away from popularly accepted formats.

A press release issued by The Open eBook Forum (OeBF), early December 2003, reports more than 1-million ebooks sold over the first 3 quarters of 2003. [1] (http://www.openebook.org/pressroom/pressreleases/q303stats.htm) OeBF 2003 third quarter analysis, based on data from ebook publishers and retailers, shows strong double-digit growth over the same period in 2002, in three aspects:

  • Number of units solds
  • Revenue from sales
  • Number of published titles

Attempts are underway to create a standard format for ebooks, notably by The Open eBook Forum (OeBF), based on XML/XHTML.

Government documents

Some government agencies have begun experimenting with the use of electronic book technologies for certain books (especially those containing legally mandated technical standards). In the case of a few books, the printing of the paper version has been discontinued to save money, and the version available on the Web is now the sole official version for legal purposes. The Manual on Uniform Traffic Control Devices is the best example of this practice.

See also

External links and references






es:Libro-e eo:E-libro fr:Livre lectronique ku:E-pirtk nl:E-book ja:電子書籍 pl:Ebook pt:Livro digital zh:电子图书


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