Despite what many people think when they encounter books about game development, this is not a book about game design, but rather an introduction to game engine architecture .This book contains a wealth of information for those acquainted with javascript programming and have at least passing knowledge of the underlying mechanics of game programming, but this is not a book aimed at amateurs. This book is designed for intermediate usage, containing numerous tidbits that are stepping stones for higher advancement. Introduction and explanation of optimization techniques, advanced spatial partioning and touch based controls for mobile devices serve as launching pads for improvements for your own game engines that you can write if you heed the author's advice.
Coming from a background of game development myself I will admit that I am fairly biased in this review, knowing near all the techniques laid out in this book, however there are a number of "Aaah" moments where I noticed small improvements I could introduce to my workflow that I usually ignore for the sake of speed such as the extensive developer backdoor and debugging code.
If I had to find fault with this book, it would be twofold .Firstly the book doesn't contain references to current advances to game engine design for HTML5 leveraging web workers, local storage and other generalized game engine design, though I can understand the time and size constraints this would impose, and secondly with the examples developed for the book. Whilst I understand and sympathize with the choices that were made, many who follow this book will probably not find the demos interesting or engaging from a gameplay and asset standpoint which may affect how they view the author's writing on game programming, but if you're willing to look beyond what has been presented to you and instead think of the possibilities of your own implementation following the lessons in this book, you will find this a great introduction to writing basic 2D engines in javascript, with enough generalised knowledge to carry over to basic engines in other languages.
Final thoughts, if you're starting out with game development and want to go on a hands on journey through basic game architecture design to help you ultimately develop your own HTML 5 games, this book is for you