Thus far, this seems to be the singular AS3 book to read. Though at times ever-so-slightly scattered, it's proven to be my essential guide to delineate areas that are either left to mystery or are just poorly-explained in other documentation. It deserves a minimum of 4 stars, in my mind, for completely fleshing out the "gotchas" for those of us coming from AS2, and making clear what are, in some instances, very fundamental but sometimes-subtle differences. At over 800 pages, it may discourage some readers, but, for me, the verbosity and thoroughness have generally contributed to my comprehension of the language.
I'd advise those with significant programming backgrounds wanting to jump in head-first to concentrate on the areas that fit your level of expertise — skim/forgo the more-remedial areas (e.g. the Arrays chapter) and the more in-depth and advanced topics. You can always drill down as you get your feet wet.