Haven't read the book yet myself (it's sitting right here on the top of my "read me" stack), but because of its focus on gaming, I'd suspect that a more general book would serve you better as a first book unless all you are interested in is gaming (and perhaps even then).
Perhaps someone who's cracked the book (or the author) can chime in with an informed response.
Bear is correct. I introduce HTML5 in an introductory chapter but much of the focus is on gaming. You might want to try something like HTML5 Guidelines for Web Developers.
subject: Is "Learning HTML 5 Game Programming" a good first HTML5 book?