In an earlier post, we talked about PDF as a file format for e-books. We discussed an important limitation of the format. It is a fixed layout format, which works very well for print, but not for e-books. Since reading devices some in different sizes, reflowing of text is an important criteria for a file format to be acceptable for e-books.
Over time various formats came up to address this issue. The one that has emerged as a standard is EPUB. EPUB uses HTML and CSS to store the content and styles respectively. It also has provision for including images, audio and video resources. It lets you include table of content and other navigational lists as well as meta-data in the EPUB file itself.
Since the specifications for EPUB are open and the basic content is stored as HTML and CSS, for anybody familiar with HTML and CSS, it is theoretically possible to create an EPUB from scratch. However, it is not a very convenient way of doing so.
Most of the e-book reading devices including NOOK, Kobo e-reader, Sony Reader etc. support EPUB as the primary format. The notable exception is Kindle, which works on its own proprietary format. However, Amazon provides tools for the conversion of EPUB to the format supported by Kindle. Hence creation of EPUB suffices for publishing on all major platforms. Plenty of EPUB readers are available for different devices, a large number of them free. So, EPUB is going to become even more popular in future.
While reflowable content is good for most part, there are certain kinds of books, where a fixed layout is the only way it can work. Comics and Graphic novels, for example. Or photo-books. What are the file-format options available for such books? We will discuss them in a separate blog post.