The writers of this book are both well established Flash Developers, both with outstanding web sites to boot. Jobe is part of the team that created Electrotank.com, and derek has his site at DerekFranklin.com. Have a look and see for yourself what the authors are capable of.
I have been using Flash since release 4 and I would like to think that I had mastered many advanced features of Actionscripting in that time. Flash MX, on the other hand, is a different kettle of fish - a lot has changed with the way that everything now works (object orientated), making it similar to the way other languages work, especially JavaScript. FMX, however, is far more powerful than JavaScript, and most other scripting languages too. There are also many additions to the scripting, not least of all the ability to use functions, at last!
All in all, whether you allready know Actionscripting, or not, you will have a host of things you need to read up on and with the recent release of MX there are few resources to do this.
'FMX Actionscripting - Advanced Training from the Source' is a great book. Suited more toward the established actionscripter, it tackles some of the more complex functions of Flash MX. XML now plays a major part in web development and as such has a rightfully earned place within MX and it is covered in the book with both simplicity and complexity. Multiplayer Flash games, as seen on electrotank.com, are covered too. Communication between languages such as ASP and PHP, the new drawing capabilities have a place, as do the concepts of controlling sound and images with scripting. Other topics covered include: Dynamic forms, data submission and valiation, external data and understanding/customization of
objects (the new smart clips)
The book comes with a CD that has all source files, part and fully completed. This enables you to complete each project in the book without having to create all non-actionscript parts, you simply enter the script. The full files can be used to compare your work to.
In my opinion this is the best Flash MX book available at the moment. There is another book which starts from a more introductory level called 'FMX Actionscripting - Training from the Source'