Posted 03 May 2012 - 04:28 PM
Fortunately, any XHTML techniques you've learned will serve you (mostly) well with HTML5 and the stuff that doesn't is easy to unlearn.
We are currently working on a 2nd edition of this book that ditches the XHTML and updates for HTML5. I'd say 85% of the book is basically the same, though, so you've learned the core basics and that will continue to serve you well and as a good foundation for learning HTML5.
I hope this helps!
Author: Head First HTML5 Programming, Head First HTML and CSS, Head First Design Patterns