I absolutely loved it, and thought be book couldn't be any better, because the huge scenes of the desert were so great at providing the post-modern directionless feeling that was needed. Well, I stand corrected. The book is amazing. It doesn't have any of the stupid crap that the movie includes just for comic relief. Basically, the point is that there are no heroes, nothing hapens, and you find yourself rooting for the characters to succeed, but success means bettering themselves, not succeeding within the plot (e.g. killing all the ragheads).
Also, alot of Marines are saying that it shows the Corps in a poor light. I personally walked away with much more respect for the Corps after watching the movie and reading the book than before. However, neither the book nor the movie is actually about war. It's about the people participating in the war and how, despite how we see them, they're human. They're not these amazing selfless guys that war movies are always about. They're just average people put in extraordinary situation, and it's absurd to expect them to be incredible soldiers. Hell, it makes me respect those who actually are far more than I used to, because it's hard to handle all the stress.