A pretty well written book, and I personally liked it a lot since I am an atheist and could see myself going - "Exactly" at various points in the book.
The book takes up the various arguments for "god" and systematically demolishes the ( usually non-existent) proofs for them. Of course the classic cop out by the believers always is - its a matter of faith, which is supposed to trump all arguments and logic. This line of thinking is also analysed and alternatives suggested, which seem as good as the god delusion.
I guess at least reading a book like this is good to remind myself that being an athiest is an option, and there's nothing particularly "holy" about people's religious beliefs. At any rate their conviction that offences to religious beliefs trump all other offences is just that - their belief. Its a topic as open to discussion as any other, and really under no circumstances can an offence to anyone's humanity overtake an offence to someone's religion.
The insistence on refusing to discuss, and keeping a holier than thou attitude is simply a sign of keeping their head firmly in the sand. And if thats the approach the believers want to take, they really should keep their hands there too!