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. I wished there was the new revision of the book to cover JavaScript 1.4. On of the co-authors of this book, Alexander Nakhimovsky, was a professor I had at Colgate University. This is a well-written book, but don't be fooled into think it's the definitive JavaScript reference. This book delves deeply into object oriented programming in JavaScript, and teaches excellent OOP techniques.