O’Reilly Media has just published EPUB 3 Best Practices, edited by Matt Garrish, who wrote much of the EPUB 3 specification itself, and Markus Gylling, Chief Technology Officer of the IDPF. I can’t think of two people more qualified to organize and oversee this work, and it was a delight to work with Matt in composing and editing the chapter that I contributed.
For some reason the book synopsis doesn’t cover the killer feature of the book, which is that many of the chapters were authored by hands-on experts in EPUB development and production.
The whole book is highly recommended, but I’ll pull out a few highlights and credits for those contributors:
Packaging and metadata: Bill Kasdorf
Bill was given the unenviable task of explaining the flexible-yet-complex new metadata options available in OPF 3.0. I love this succinct summary of the various components of the OPF, which can be difficult to explain to beginners:
Which EPUB is this (“identifiers”)? What names is it known by (“titles”)? Does it use any vocabularies I don’t necessarily understand (“prefixes”)? What language does it use? What are all the things in the box (“manifest”)? Which one is the cover image, and do any of them contain MathML or SVG or scripting (“spine itemref properties”)? In what order should I present the content (“spine”), and how can a user navigate this EPUB (“the nav document”)? Are there resources I need to link to (“link”)? Are there any media objects I’m not designed by default to handle (“bindings”)?
I recommend particular attention to the section on EPUB 3’s solution to unique identifiers and document updates. Too many retailers still have substandard responses to book updates, which often boils down to either not supporting updates at all, or clobbering user annotations and bookmarks.
When technologists—or reading systems—say an identifier uniquely identifies an EPUB, they mean it quite literally: if one EPUB is not bit-for-bit identical to another EPUB, it needs a different unique identifier, because it’s not the same thing; systems need to tell them apart. Publishers, on the other hand, want the identifier to be persistent. To them, a new EPUB that corrects some typographical errors or adds some metadata is still “the same EPUB”; giving it a different identifier creates ambiguity and potentially makes it difficult for a user to realize that the corrected EPUB and the uncorrected EPUB are really “the same book.”
Navigation: Matt Garrish
The majority of EPUB 3 publications produced commercially are likely to include not one but two tables of contents (the EPUB 3 Navigational Document and the EPUB 2-era NCX for backwards compatibility). Matt provides compelling use cases for the new form: marking up deeply nested TOCs, linking printed page numbers to the EPUB edition, and providing the much-needed Font embedding: Adam Witwer
Perhaps the most practical chapter in the book, Adam discusses the ins-and-outs of font embedding from his perspective as a publisher, writing:
Font obfuscation has been the source of much confusion. If you dig around the Web, you’ll find plenty of blog posts and forum chatter full of confused and frustrated ebook makers trying to make sense of it all. The confusion stems largely from the fact that, until recently, the IDPF and Adobe had competing font obfuscation algorithms, and reading systems supported one or the other. If you used the Adobe obfuscation method, your embedded font would render correctly on maybe the NOOK but not in iBooks, and so on.
Font embedding in ebooks is a messy and confusing full of traps for the unwary; it’s telling that Adam’s chapter has more footnotes than any other.
Global language support: Murata Makoto
This chapter will be a lifesaver for those publishers struggling to produce correctly formatted ebooks for the Inner Mongolia market.
(Seriously, there’s invaluable information here on EPUB 3’s support for Asian languages, right-to-left scripts like Hebrew and Arabic, and the interesting edge cases that emerge in rendering numbered lists and hyphenation. It’s worth reading just for a high-level overview of the immense diversity in modern human writing systems.)
Accessibility, validity, et al
Last but absolutely not least, the chapters on Accessibility are must-reads for anyone producing ebooks seriously. I’m not sure there’s a better reference on advanced topics like EPUB 3 text-to-speech (TTS) support, media overlays, and other features that — while designed for the print-disabled — offer tremendous options for creativity and truly enhanced digital-native publications. The section on understanding errors from epubcheck is also extremely welcome, as even experienced developers can sometimes be baffled as to the underlying causes of validation failures.
EPUB 3 Best Practices is an absolute must-have for anyone in our industry. Highly recommended.
Safari Books Online subscribers can read the entire book as part of their subscription.