This is the most concise and focused book on JavaScript. I had tried two other highly recommended books prior to this one, and both left me with many unanswered questions and an image of JavaScript of being an extremely awkward and unmanageable language. This book made everything crystal-clear. There are practically no aspects of the language not revealed in the book. After reading it you will have a structured and in-depth understanding of JavaScript, including its most subtle topics.
Examples are short and very helpful.
Do not hesitate to buy it. This book is very thorough and well written, but it is not a book for the beginner programmer. A review from New York Good book, but too complicated. It is a good book. It is a book for people that KNOW JavaScript quite well, for people who want to learn more about it in depth.