I'm a Flash developer/animator and AE newcomer. After Effects is a very deep program, and this book covers a lot of it's capabilities. As someone just starting After Effects work, it's a great intro. I don't have any other books to compare it to, however (like I said, just starting out).
One thing that does concern me a bit: while following lesson instructions you are asked to do some routine things that will make sense to someone used to working in Flash or a 3D animation program, and only a cursory explanation is given as to why you would do this. Mostly workflow and best practices kinds of stuff. While I did not have a problem with it due to related experience, I think someone just starting out cold might. That said, it is rare for me to be able to work through the entirety of a book of this type. It's nice to have different projects for each lesson; many books of this sort seem to create a movie project replete with every feature the program has to offer that you follow from beginning to end. This usually makes me lose interest -- especially if the project is incredibly lame. These projects are all pretty lame (visually lame - they are informative and useful) but you only have to deal with a particular project for a few hours and then it's off to new footage and assets.
I haven't had any problems with any of the lessons or files, except:
one JPG that was corrupted on Lesson 5 (there are more to choose from , not a show stopper).
In lesson 8, Creating a Walk Cycle: One of the X positions on the graph on page 222 is incorrect -- it needs a "-" sign before the coordinate. I think it was for the torso at 1:00, but I can't recall for certain.
In lesson 11, Positioning 3D Elements: the initial composition should be set to "square pixels" instead of the stated "D1/DV NTSC" in order for the steps provided for correct 3d positioning to work accurately on your monitor.
Not huge errors for a book of this type, but I would have expected Adobe to hand this to a neophyte for testing -- these should have been caught easily by someone following the instructions.
I have not had any crashes or hardware related problems. This is a demanding program, however. I'm using my work machine (Mac Pro tower, 8 cores, 6GB RAM, OS X Leopard), which is a behemoth. I don't know how my home machine would handle it, or the stability of the Vista or XP versions.