What is EPUB?
XML-based, EPUB is the most widely-supportede-book format other than PDF; that is, it is supported by almost all hardware and software (desktop) readers except for Kindle(whose proprietary formats often contain an originatingEPUB file anyway).
EPUB 2 was the industry standard as of 2007, being supplanted in 2011 by EPUB 3, now on its second minor revision. The EPUB 3.0 format was developed to address the perceived shortfalls of its predecessor, including:
Lack of suitability for high-design publications such as graphic novels and children’s books.
Lack of support for equations formatted as MathML,meaning that equations were included as images, which don’t always render clearly.
So EPUB 3 has been around for eight years, but many publishers worldwide are still using EPUB 2. Why? Simply put, for many publishers (and self-published authors), EPUB 2 still meets all their needs. It can render reflowable text, tables and images in a way that works across the whole device spectrum, right down to the lowliest (oldest) devices, because – while those devices might be regarded as obsolete by technophiles and those consumers who must have the latest gadget even if their old one still works –many people still use them, with the logic that ‘if it ain’t broke, don’t fix it’.
This leaves publishers in the position of having to cater to the lowest common denominator. Newer devices are always backwards-compatible, but older devices just can’t parse some of the under-the-hood wizardry of the newer formats.
So which format should you choose for your eBook?
In terms of cost – and leaving aside Fixed Format, which we’ll deal with in a separate post – there’s really no difference in the cost of converting a reflowableEPUB 2 or anEPUB 3. The difference ultimately comes down to whether you need EPUB 3’s special capabilities, e.g.:
The ability to set mathematical equations using MathML.
The option to include audio and video content.
Accessibility metadata – letting your readers knowspecific information about the usability of your publication, allowing them to decide whether your content is appropriate for their needs.
Including ARIA descriptions andimproving the accessibility of images by using aria-describedby (see here).