It’s easier to tell you want this book is not.
It’s not a book for beginners. But if you know some JavaScript, you’ll get a better practical and theoretical understanding from this book.
It’s not a “bible”-type book. It doesn’t try to tell you everything about JavaScript.
It’s not a cookbook. It doesn’t give you a few recipes, which leave you confused when you want to make your own confections.
This book teaches many of the most practical concepts you’ll need to know to use JavaScript. It’ll leave you feeling confident that you can do this yourself.
Highest praise I can give: This is the only Web scripting/programming book I have read cover-to-cover.