Personally, I'm not keen on this approach. The author takes you step by laborious step through the process of creating a Flash web site. The result is that the underlying principles that you are trying to learn get lost in a heap of application-specific details. It's difficult to separate what you want to learn from what is only relevant to the author's chosen site.
Here's an example. How do you create a gradual change ("tween") from one shape to another? Easy-peasy: you just create your two shapes, several frames apart on the same layer, and, in the Property Inspector, set the "tween" property to "shape". That's it. But Chrissy Rey takes nine pages to explain that! She starts by saying you must create a rectangle exactly 25 pixels square, placed exactly at the center of the frame... but this is of course unnecessary. You can tween any two shapes you like.
One result of this is that the contents get muddled. In the section about shape tweening you find loads of details about how to make sure a rectangle is square, etc, which would be better covered in the section on drawing shapes.
A few further irritations.
(1) There are quite a lot of errors. When you are trying to learn something new, you don't want to be wondering "does she really mean this, or is this another typo?".
(2) Why does the table of contents not give page numbers except for the main sections? If I want to find a particular topic, I want to know better than "somewhere between pages 256 and 310".
(3) I don't go for the pale lilac ink used for actionscript. Color can be useful, but this hurts the eyes.
(4) It is very repetitive. She frequently says "type in this text" then shows the text you are to type (in lilac), then shows a screen shot of what the text looks like in the editor, then says "this is what the text should look like after you have typed it in" and then shows the same text a third time, again in lilac.
(5) The example site that the whole book is built around is, in my opinion, not suitable for a Flash web site. In general, building entire sites in Flash is not a good idea. Most of the content could be done better (more quickly, more efficiently, more accessibly) with standard technologies (html, css, javascript/ecmascript). Flash should only be used for those parts of a site where its capabilities are required (animations, video, client-side real-time program control of multimedia content, accessing XML data sources, etc). I would strongly recommend all web authors to read "Designing with Web Standards" by Jeffrey Zeldman (New Riders) before embarking on a Flash site.
I think a better introduction to Flash MX is Katherine Ulrich's "Visual Quickstart Guide, Macromedia Flash MX for Windows and Macintosh" (Peachpit Press). Cheaper too.
Summary. If you enjoy working steadily through a complete example, starting at page 1 and going through to the end, then this book will probably suit you. If on the other hand you want to pick up the essential principles quickly so that you can apply them to a different application, then look elsewhere.