EPUB 3 books can be created from HTML5. The same principles for creating well-formed, semantically sound web content apply.
HTML 5 semantic markup gives meaning to otherwise anonymous containers or text structures. For example, use the
<section> element to denote changes in topic, or
<aside> to indicate content that is secondary in importance.
EPUB 3 also provides semantics more suitable for publications. In addition to using HTML 5 semantic markup, you can describe the same HTML 5 markup as being chapters, or as a sidebar.
Here is an example:
<section epub:type="chapter"> <h1>Chapter 1: At the Start</h1> We always start with a good idea. <aside epub:type="sidebar"> In 2013, 9 out of 10 ideas were great. </aside> </section>
The “EPUB 3 Content Document” article by Matt Garrish is a good place to start learning about semantics in EPUB 3: http://epubzone.org/news/epub-3-content-documents.
Source: Floe project. Edit this page on GitHub.