This book walks through creating a 'bubble shooter' browser game, similar to Puzzle Bobble or Snood. It uses jQuery and Modernizr script libraries to avoid browser-specific concerns, and Modernizr for loading scripts. The first version uses the DOM to position and animate game elements (bubble), and shows custom animation in jQuery. It discusses which animations are possible in pure CSS3, as well.
I found it interesting that the book moves on to a second version, where the game board is completely contained in an HTML5 Canvas, and all animation is handled inside the canvas, using calls that are compatible with the DOM version - so the older version can run on old browsers that don't properly support Canvas. That structure seems useful to think about.
I would have liked to see a more complex game, like a platformer or side-scroller, but that would have swelled the book and I bet the complexity was too much for the goals of the author.
Overall, a good beginning game programming book - but definitely a starting place to jump off into more complex issues if you want to work on any sort of releasable, 'real' game.