I wasn’t a big fan of Dawkins’ "The God Delusion" as, apart from a few anecdotes from Dawkins experience, there was little new in it as the arguments for god that are expressed and refuted have been refuted countless times. If you’re looking for something that generally summarizes why there’s probably no god, then this might be a good choice. As an atheist I too was able to "poke holes" in his thesis, not because he was wrong but because having been a Catholic, I understand the religious experience more than most. The religious experience is entirely subjective, and Dawkins’ arguments are objective. The arguments for the existence of gods that Dawkins chose to refute were the ones that attempted to be objective. In other words, I kind of felt that Dawkins (along with other atheists in general) focused too much on objective evidence and not enough on the "reasons to believe" that religious people have. That’s just my opinion. If, however, you’re unfamiliar with the various arguments for/against the existence of gods (ie, argument from design, teleological, etc), then this book is a really good primer.

Dawkins science books are much better reads, in my opinion. "The Selfish Gene" is a very good explanation of evolutionary theory and "how things came to be this way" from a biological and to a lesser degree moral/cultural level. I greatly prefer reading books about "how things came to be this way" as I’m more interested in learning what we know about that than in academic debates over what we believe about things what we can’t possibly know about.

The "four horsemen" (as they’re called in the blogosphere) of modern atheist literature are Dawkins, Sam Harris ("Letter to a Christian Nation"), Christopher Hitchens ("God is Not Great") and Daniel Dennett. Of the last three, I’ve only read articles they’ve written or watched lectures or interviews they’ve done, not read their books.

"Guns, Germs and Steel" is an excellent book about the spread of culture and civilization and how ideas, languages, cultures and people have spanned the globe. Its author Jared Diamond is an atheist but he doesn’t write about atheism.

Between "The Selfish Gene," "Guns Germs and Steel," "Ishmael" and some book on modern ideas on cosmology and nucleosynthesis, you have a pretty solid and simple model of how things came to be this way. Even if you don’t agree with all of it, there certainly aren’t any god-sized gaps that need filled.

Hope that helps. Enjoy! I greatly respect your ability and desire to challenge your assumptions.

Edit:

I totally appreciate your new mantra and agree with it myself. I think we should also assert our ignorance. However, the reason why people took issue with (or got confused by) your wording is the same reason I take issue with the "turning your back on Jesus" comment. Cognitive dissonance is a very powerful thing.

I didn’t "turn my back on Jesus," I sought knowledge as a form of worshipping God. If God gave me this brain, surely using his gifts is a form of thanks and praise. I was very nearly a priest at one point in my life, but at some point I realized I didn’t have any good reason to believe and, in consequence, I didn’t.
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I’m an atheist, an agnostic and an animist.

My work-in progress blog: http://www.noonespecial.ca

As a Christian, one who truly believes the bible and can say that Jesus is my Saviour and that He has forgiven me all my sins I would like to recommend a very small book to you. It is called How Good is Good Enough and it is written by Andy Stanley. It can be bought singly, in packs of 6 or in bulk and is not expensive. It is easier to obtain in USA than it is in UK. Someone used to sell them on Ebay.

P.S. I’m not surprised that the Christians did not understand what you meant. You don’t seem to understand it yourself and, even in your explanation, you say "When I said "non-believers of all faiths" I meant people who were Christian at one time but turned their back on Jesus and became non-believers." There is no such person as a Christian of all faiths. Christianity is one faith, Buddhism is another, Islam is another etc. etc. If you want sensible, literate answers to questions please make the question clear. What I think you really meant to say was "ex-Christians of all DENOMINATIONS". Now, those words I (and my fellow Christians) would have understood.
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Good luck and enjoy!
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Age of reason…http://www.gutenberg.org/etext/3743
Common Sense…http://www.gutenberg.org/ebooks/17607

This is the ultimate cult-breaker folks… the original and most powerful religion destroyer – and it’s a load of laughs.
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