I've now read five titles on HTML5 game development, and while each has their redeeming qualities and high points, Jacob Seidelin's fine work is an absolute must-have. This isn't for the novice or beginning dev looking to add a new arrow to their web programming quill - this is a healthy discussion that tackles specific challenges in creating rich, engaging games for the browser environment. Seidelin greatly emphasizes the web's key advantage of being accessible via browsers on the desktop, smartphones, tablets, and hopefully soon, interactive TVs.
The book doesn't spend time discussing game theory and doesn't go into exhaustive detail with APIs for canvas and multimedia, it states the objective in building a puzzle game and then attacks the problem by building-out each of the components and subsystems. Each chapter is very logically-organized and well-written, neither too short nor not overly verbose. It leverages techniques for multiplayer games like Web Sockets and Web Workers and uses slick techniques to take advantage of local storage for a real console feel. The animation and WebGL chapters are very much appreciated, too.
But the book's finest hour is its hearty chapter dealing with the nuances of mobile games for iOS and Android. This chapter is essential reading, featuring material not found in wide distribution with most titles out there at the moment.
This book is so good, I'd recommend owning it AS A BOOK. With maybe an electronic copy as a backup. :)