In part a protest against the implied basis of the book dorkins has written, I am refusing to read it (1). I do not believe this disqualifies me from criticising it, as long as I stick to criticising the basis of the book, and use whatever quotes from the book I get from reliable sources. Now, it is a Provable Fact that the existence of God cannot be proven, nor disproven. As a corollary to this fact, talk of the improbability, or probability of the existence of God is completely meaningless. Therefore, any author who goes to any length to convince someone otherwise is either delusional (2) or a fraud. From this, I can speculate that since he tries to convince the would be reader anyway, that a lot of his "logic" and "reasoning" is not watertight. I would recommend a would be critic to start as given that God doesn't exist, and that therefore those that believe in God are in fact delusional. His assertion that "religion is bad" and that "the mistaken belief in God is the root of the badness of religion" appears to be a theme he talks about, but never gives tight definitions and solid reasoning to back it up. If "bad" and "good" are pretty well taken care of by our moral sense, these are extremely arbitrary assertions.
(1) I might read parts of the book down the track, who knows?
(2) This is not really the "stick him in the mental asylum" delusional, but a common, fairly harmless delusion with anyone with a non-self-consistent World view.