Outstanding summer fare with an excellent repeatability factor. If you want character development or angst over the human condition, definitely go see something else. If you want pure, mindless fun, this one is the "Destroy All Monsters" of action movies.
No one can screw up a good book like Hollywood. Gone is the books' self-effacing humor, replaced by overblown melodrama of groaning proportions. If you've never understood what a critic means when he/she says "this movie takes itself too seriously", then by all means go see this movie for your own enlightenment. Many "minor" details were omitted which become important in the later books, strongly suggesting to me that the screenwriter hasn't read all the books. Other than for the aforementioned enlightenment, stay away from this turkey.