Really good book
This book is really good, which is the reason I started to buy Training from the source books. I was disapointed by others of this serie. but not by this one.
As opposed to most of them, this book isn't on one big project building from chapter to chapter. It is divided into small projects, sometimes even more than one in a chapter, more like the Classroom in a book from Adobe serie.
Covers a lot of topics and covers them well with relevant exemples. Of course, when we talk about ActionScript, it's not for Flash beginners (unless you know not much about Flash but does know about programming languages, like JavaScript for example).
In Flash MX, it's still the old ActionScript 1.0, so you may want to refresh in the Macromedia/Adobe documentation if you expect to build with ActionScript 2.0 or 3.0 (in fact, for ActionScript 3.0, you'll probably want to consider another book... for ActionScript 2.0, if the same book is available for Flash MX 2004 and/or Flash 8, then go with it...).