I have passed the w3c test for xhtml so I am very knowledgeable but some rules have changed.
For instance instead of using an image tag in <section> you only use css to put up the image. So there is no accessibility for disabilities, like alt or title in the image. I guess, and only guess, you can cheat and type in a <p> or <h1> tag in the section with span to hide the information, but I think that is only for search engines and not for accessibility.
So I am asking what is your html5 book about, since I don't need to learn html, is this my kind of book?
Joel Storchan