I have recently read three books written from an atheist perspective concerning either religion or God. Those three books are "The God delusion" by Richard Dawkins, "Letter to a Christian nation" by Sam Harris and "Breaking the spell" by Daniel Dennett.
I shall give my thoughts on these books in order. Firstly "The god delusion":
The God delusion is well written but somewhat long. Dawkins it seems has poured all his thoughts about religion and the non existence of God into one book. The first thing to note therefore about the book is that it doesn't have very much space devoted to the actual arguments for and against the existence of God. Dawkins argument is little more than the standard:
God is an incredibly arbitrary assumption that is not required to explain the universe. Occham's razor is fundamental to science and its application here means we must go with the theory (until new evidence comes in) that there is no God.
Dawkins does not justify the unfettered use of occham's razor. This is not unreasonable. As far as I'm aware occham's razor has been neither refuted nor proved. Indeed the question is probably currently unanswerable as mathematicians don't have a consistent theory of probability.
Dawkins spends a lot of time dealing with issues which he himself regards as irrelevant to the central question. These include "Can scientists have a sense of wonder?", "Can atheists be religious" and "Where does religion come from?" which he answers yes, yes and cultural evolution. Unfortunately Dawkins takes a rather harsh stance on various individual religions descending at times into ad hominen attacks and the use of anecdotal evidence.
Overall this is a good read making some enlightening arguments (the vast majority of which are sound). However, it seems unlikely to convince a strong believer to renounce their faith as it is too likely to mortally offend them.
Secondly "A Letter to a Christian nation": I don't want to mince my words here. This book is a rant. A rant that may amuse some hard line atheists but a rant nevertheless. Its not going to change anyones mine as it has almost nothing in the way of actual discussion or argumentation.
Thirdly I come to "Breaking the spell". This is a superb book. Its not written to present arguments for an atheist position but it is the book most likely imho to convince someone there is no God (and the only one likely to work with a moderately religious individual). It is flawlessly tactful, it does not make any assumptions that a religious reader is likely to object to. The premise of the book is the following "Let us see how religions could be understood if one did not assume the existence of God". It then addresses many questions necessary for such an understanding and carefully weighs the different positions against one another.
On the idea that religion is something that should be left to the experts (priests, rabbis etc.) he has this to say: "We would never let business tycoons get away with saying that since we weren't plutocrats ourselves we couldn't hope to understand the world of high finance and were hence disqualified from investigating their deals.
All in all whether you're looking for a good book discussing religion from a naturalistic stance or a book to give to the strongly religious person in your life this is the book to go for!