When I first started working with this book, as a developer myself, I thought it a bit of a cheat. The author's built their own framework which you use to do the clever stuff whilst you focus on the principles involved in building *games*.
However, the more I got into the book the more I appreciated their doing so. Browser based development's a pain as every different browser interprets your program differently and creates new ways to screw up your code. The framework handled all of that, without taking away the actual coding you need to get the most from HTML5 and the games themselves to run.
As such, I learnt a lot about the capabilities of HTML5, was able to get programs up and running quickly ( having zero attention span, that was *very* important ), didn't need to faff about with the low-level 'tech stuff if I didn't want to.. and had a lot of fun. :)
For those budding hackers, the full framework source code is provided, with some good guidance as to what it does and how, so if you want to it's very easy to quickly take your coding to the next level without having to start from scratch.
No I didn't get the wrong book. The title is HTML5 Game Development for Dummies. Yes it's about game programming, but the HTML5 element's are mostly hidden from view within the game engine and only vaguely mentioned at the very end.
However If your new to Java-script and like the idea of learning by creating games, I would recommend it.