12 Ebook file formats

It’s important that you understand the following about file formats:

  • That there are hundreds, if not thousands, of file formats
  • That a file format is just a container for a particular type of information
The following background reading will give you more insight into file formats:
Wikipedia’s list of file formats. The essential lesson here is that file formats are tools designed for a purpose, and there are many things we do with computers. Notice how the INDD (InDesign) project format is classified as a “desktop publishing” format and how there are many more formats than MP3 for audio files.

Study component

There are many formats in which one can read ebooks. The formats we deal with in this chapter are those that are in popular use in the publishing industry as an ebook end-format: PDF, EPUB and the Kindle formats.

While any electronic file format can be used to publish ebooks, an investigation of ebooks in practice reveals two approaches to production: ebooks that are book-like and ebooks that are not book-like.

A book can be a series of image files, a plain text document, a Microsoft Word document – even an immersive 3D environment. To demonstrate this point: the Mobileread community wiki lists 41 ebook formats – including the .exe, or executable format used to launch applications in Microsoft’s Windows operating system.

Some of these formats have been discontinued (for instance, Microsoft’s .lit format), some have a specific user base (for instance, the Comic Book Zipped format .djvu) and others have undergone many changes in use and ownership. For instance, the .mobi format was developed and used long before Amazon purchased and customised it. This variety of formats – and their constantly changing nature – can offer insights into the intended function of ebooks and, hence, how ebooks can be enhanced.

Book-like formats

In 2012, three book-like end-formats dominate the ebook landscape: PDF, EPUB and Kindle (a general term for Amazon’s MOBI, AZW and KF8 formats). These formats are targeted by book publishers because of organisational support, ease of creation and ubiquity. Most significantly, these formats can be wrapped in digital rights management, which is an important (and debated) function for rights holders.

Each of these book-like end-formats is better described as a platform (Tonkin, 2010), and the latter two are based on the same technologies that drive publication on the WWW, namely HTML, CSS and XML (Tallent, 2010) . PDF remains a popular choice since it is integrated into popular document authoring software.

It is important to understand these formats because they can provide guidelines to which of the identified ebook enhancements (described in the methodology section) can be implemented in practise.

Another “format” targeted by the book publishing industry is the application, described in the next section.

Non book-like formats:  applications

Book-like content is being prepared in non book-like formats, the most recent of which are applications (apps) on mobile computing platforms. Publishers are experimenting with content delivery in the form of applications (apps) over these platforms – for instance, the Apple iTunes store or the Kindle app store.

An app, as described in this section, can be considered standalone and non book-like, whereas book-like ebooks described earlier can be seen as residing within apps. This distinction is important because it demonstrates how the line between book-like formats and non book-like formats is blurring (Kostick, 2011). For instance, the Kindle app for Apple’s iOS operating system reads content in a book-like format – .mobi files. A publisher could release the same content as a native iOS app – as was the case with Our World (Kostick, 2011).

Book-like ebooks (for instance, Amazon’s .mobi and KF8 formats) are increasingly networked and interactive – enhancements that are associated with applications, not books. For instance, EPUB3 (finalized in 2011) supports JavaScript, leading to the ability to deliver scripted documents in a book-like format.

In addition to the above approaches to ebooks, publishers are considering the enhancement of ebooks – which is the main focus of this study.

1. GuidingTech (2013). GT Explains: What is the Difference Between EPUB, MOBI, AZW and PDF eBook Formats? Available online: http://www.guidingtech.com/9661/difference-between-epub-mobi-azw-pdf-ebook-formats

2. Kostick, A. (2011). Digital Reading: Is It an E-Book or “Just an App”? Comments on Our Choice Give Detailed Feedback. Digital Book World. Available online: http://www.digitalbookworld.com/2011/digital-reading-is-it-an-e-book-or-just-an-app

3. Tonkin, E. (2010). eBooks: Tipping or Vanishing Point? Ariadne. Available online: http://www.ariadne.ac.uk/issue62/tonkin



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