The God Delusion is an extended diatribe against religion in general and belief in God in particular; Dawkins and Daniel Dennett (whose recent Breaking the Spell is his contribution to this genre) are the touchdown twins of current academic atheism.
Dawkins has written his book, he says, partly to encourage timorous atheists to come out of the closet. He and Dennett both appear to think it requires considerable courage to attack religion these days; says Dennett, "I risk a fist to the face or worse. Yet I persist." Apparently atheism has its own heroes of the faith—at any rate its own self-styled heroes. Here it's not easy to take them seriously; religion-bashing in the current Western academy is about as dangerous as endorsing the party's candidate at a Republican rally.
The God Delusion is full of bluster and bombast, but it really doesn't give even the slightest reason for thinking belief in God mistaken, let alone a "delusion." The naturalism that Dawkins embraces, furthermore, in addition to its intrinsic unloveliness and its dispiriting conclusions about human beings and their place in the universe, is in deep self-referential trouble. There is no reason to believe it; and there is excellent reason to reject it.
This comes from an article by Alvin Plantinga, published in Books and Culture, March/April 2007. You can find Plantinga's homepage here.