Before jumping right into the best practices, let’s take a brief moment to answer the question: what exactly is an EPUB?
If you’re already familiar with the inner workings of the format, whether from creating EPUB 2 content or experimenting with EPUB 3, you can safely skip ahead to Chapter 1, but this introduction will take everyone else through a quick tour of the format (at the macro level, instead of the micro level to come) to see how the pieces fit together.
Since you’re reading a book about EPUB, you must already be familiar with the term, but you may have seen or heard it incorrectly being used as a synonym for ebook (as a shorthand for talking about electronic books). Although the two terms share a common relation in electronic book production, they aren’t interchangeable. EPUB is a format for representing documents in electronic form. Ebook, on the other hand, is just an abstract term used to encompass any electronic representation of a book, including formats such as PDF, HTML, ASCII text, Word, and a host of others, in addition to EPUB.
EPUB is designed to be a general-purpose document format, and it can be used to represent many kinds of publications other than just books: from magazines to newspapers to journals, and on through office documents and policies and beyond. Just about any document type you want to distribute electronically can be represented as an EPUB. Likewise, this book is not just about how to create books in electronic form, but how to optimally use the EPUB format for any content production. A natural bias to book production will be evident at times, but recommendations should be read as publication-agnostic.
On a practical level, EPUB defines both the format for your content and how reading systems go about discovering it and rendering it to readers (we’ll avoid the word display for what a reading system does with content, because EPUBs aren’t only for the sighted and don’t contain only visual content).
But perhaps the best way to understand what goes into an EPUB is to quickly break down the creation process:
This manual process is not one you will typically carry out in full, because there are programs that allow you to focus on creating your content while taking care of the export and packaging for you. It’s invaluable to get clear in your head, though, because content and the package document are interrelated in many ways that will be explored throughout this book.
If you read the previous numbered list in reverse, you’ll also understand how reading systems work: they examine your ZIP container, determine it’s an EPUB, find the package document, and from there discover how to render the resources to readers.
The other aspect of EPUB to understand before getting started is that it draws many of its capabilities and its versatility from web technologies, but the Web alone doesn’t tell the whole story of EPUB. Without the complementary technologies the EPUB format brings under its common umbrella, the ability to create distributable publications would be much more complex.
Some of the technologies used in EPUBs have been specially developed by the International Digital Publishing Forum (IDPF), but most of the standards that have been leveraged are internationally recognized. The key ones you’ll find in EPUB 3 publications include:
You’ll learn more about how to use all of these technologies as you progress through the chapters.
The EPUB format is specifically designed to be free and open for anyone to use without having to sift through a litany of patent encumbrances and restrictions. EPUB’s widespread adoption has been due in no small part to the fact that basic text editing tools can be used to create publications, and the EPUB 3 revision of the specification has not deviated from this core tenet.
But that’s really all there is to an EPUB file under the hood. If you feel comfortable with the concept of an EPUB as a predictable, discoverable container of your content, you’re ready to begin tackling the best practices.