The writing's pretty thin in places and the jargon comes heavy. Concepts are presented hierarchically rather than cognitively (e.g. the chapter on components immediately dives into how to insert them into a Flash movie without first explaining what they are). Also, be warned that the sample files and source code isn't easily accessible -- there's no link given to the book's website, and if you go looking at the publisher's site you get a large zip file that's missing files referenced in the text.
If you're already extremely familiar with Flash MX, this book may be fine for you. If you've had only passing contact with Flash, or are upgrading your knowledge from a previous version, save yourself the grief.