I would strongly recommend against the God Delusion. It's an extremely frustrating book to read as a theist: you start swearing at the book before you get out of the prologue.
Incidentally, I think that Mere Christianity is a bit outdated. Its whole argument from metaethics has kinda died with the advent of evolutionary psychology. The Screwtape Letters is far superior.
I recommended The God Delusion - I'm not sure if that's the best choice given the above intent, but it's what came to mind on the spot.
The problem with that book is not just that it will activate people's defense mechanisms, as some people have already noted, but that these defense mechanisms will often be, on the whole, a largely correct reaction. Significant parts of that book are nothing but ideological propaganda that attacks some metaphysical systems in favor of others, and when people get a visceral reaction that they're being propagandized and not enlightened by the writer, it's a correct intuition, even if it proceeds from spontaneous mental heuristics and not a rigorous logical analysis.
Even setting aside the issue that Dawkins is selling his own metaphysics in an underhanded way, as writers in this genre typically do, many of his arguments are full of errors of both logic and fact that clearly betray his ideological biases. (This is especially cringe-inducing when he takes a superficial and caricatured knowledge of history and colors it with his ideological preconceptions.)
(For full disclosure, I haven't read all of that book, but even if the remainder is much better, what I saw is enough to draw the above conclusions.)
I had good results with The Moral Animal (a good intro to evo psych). It might be easier to challenge some of the foundations upon which theism rests and let them draw their own conclusions than to attack theism directly and activate defense mechanisms.
The thing about books like The God Delusion is that they activate his mental defense mechanisms to prepare himself for any well-thought out, logical arguments. You need to start with something which isn't as blatantly screaming "this book wants to destroy everything you care about because it merely happens to be right!" So I'm somewhat surprised people haven't realized this and gone with the following option:
Gödel, Escher, Bach (by Douglas Hofstadter)
The brilliant thing about this book is that it subtly changes people's worldview without them eve...
As someone who has done more reading in this space than I should have, I recommend Loftus et al - The Christian Delusion or Ehrman - Jesus, Interrupted.
How about Carl Sagan's The Demon-Haunted World ? IMO it is written better than The God Delusion, and it's more fun to read.
Julia Sweeny's Letting Go of God was also very entertaining, though perhaps it's best to get it in audio format. She reads it extremely well.
On the other hand, I'd can not recommend using Sam Harris's The End of Faith. It just reads like an angry Internet rant... I'm kind of surprised that the book is so popular.
And if you're looking for something subversive, there's always fiction ! C.S.Lewis isn't the only one with tricks up his sleeve. I'd recommend Roger Zelazny's Lord of Light, which is one of my favorite books of all time.
I found The God Delusion to be incredibly overrated. It's horribly organized, much of the material is uninteresting to people already familiar with standard anti-Christianity slogans, and its main argument for the non-existence of God (The Ultimate Boeing 747), while valid, lacks the punch of Occam's Razor or The Problem of Evil.
If I was going to recommend a book I would recommend Why Won't God Heal Amputees?, which has got to be the most accessible text arguing for the non-existence of God I have ever read. The last two chapters are annoying as hell, thou...
If by "high regard for the Bible" he means inerrancy, I recommend The Human Faces of God as a first step.
It covers disturbing passages that I believe damage the credibility of the Bible as a whole. Biblical genocide, slavery, propaganda, early Israelite polytheism, contradictions, and failed prophesies of Jesus are all discussed with footnotes to additional literature. Most of this material is "standard fare" among critical scholars - even the idea that Jesus was a failed prophet - but church-going people are still in the dark on most...
If you are looking for the "best argument from the other side", then The Blackwell Companion to Natural Theology by William Lane Craig and James Porter Moreland is probably the best place to start.
As far as atheism goes, I don't think The God Delusion is the best way to go since much of it involves arguments showing how religious beliefs are bad for society rather than false (which, in this context, is mostly a distraction). Instead, I would recommend Atheism: A Philosophical Justification by Michael Martin.
I'm just curious, have you taken any of the suggested book choices and redacted The God Delusion as your recommendation? Are there any other rules in your reading exchange, like say meeting once for each book and discussing it together? Or timelines for completion?
In the spirit of experiment we agreed to a "trade" - he would read (thoughtfully and with an open mind) a book of my choosing on reasons to doubt faith, and I'd do the same with a book he chose on Christianity.
Can that really be worth it? It seems disproportionally too costly for small expected gain.
Exchanging books with a random theist - probably not worth it. In context of a specific social relationship, might be worth it.
I think Dallas is going in the right direction here. It's not enough to convince someone that God is impossible- you need to give them a replacement. (And convincing someone that the Church is a harmful force- when they don't get the impression their local church is- is difficult and probably not worthwhile.) For example, as mentioned elsewhere the primary argument of Mere Christianity is probably "Christianity is an optimized meme for getting humans to believe it- that's evidence for humanity being built around the meme." The counterargument is ...
hmm... god delusion generally wouldn't be at the top for "best arguments" for atheism. I'd go with something like the Atheism: the case against god or if he'll read a tome you have Atheism:a philosophical justification, the impossibility of god, the improbability of god. These are all pretty high level philosophy books but they are the best and strongest books out there. Did your friend really recommend mere Christianity for best argument on his side?
Lewis doesn't argue that the trilemma proves Jesus was God - he uses it to dismiss the wishy-washy agnostic position of "Well, Jesus was a great moral teacher, and worthy of respect, so whether he was God or not doesn't matter."
Lewis' position is "No, hang on a minute, this is someone who's spouting moral platitudes that everyone already agrees with, not anything new as far as the morals go. But he's also claiming to be God - he's saying, over and over again, that he is God. That leaves only three options, really - either he's actually God, or he's a liar, or he's deluded. Whatever he was, he wasn't an exceptionally decent human being, so get off the fence."
Judging by lukeprog's account here, and the video he links here, and also accounts by several people on LessWrong, a grounding in rationality and science seems effective in dissolving theistic beliefs without even paying them any attention. On that basis I would recommend the Sequences, or Eliezer's books in preparation, or rationalistic sensawunda material like Carl Sagan or Feynman explaining not just how the universe works but how we know it.
I haven't read through it, but based on the description, Why I Became an Atheist by John W. Loftus may be a good choice.
In an Open Thread comment beriukay mentioned that he's reading C.S. Lewis' Mere Christianity. I've been reading it too, for interesting reasons.
In my case it so happened that I started discussing faith with a long-time online friend whose spiritual views I didn't yet know, and he turned out to be a Christian with a high regard for the Bible, who also has an interest in science. As our discussion turned to our readings on spirituality, I acknowledged (I think it was me) that I probably spent more time on books that reinforce my point of view than on books that challenge it, perhaps a case of confirmation bias. (I've been exposed to many poor arguments for Christianity, and dismissed them; but possibly that was largely a function of having started out with that bottom line already written and picking arguments I wouldn't have much trouble refuting.)
In the spirit of experiment we agreed to a "trade" - he would read (thoughtfully and with an open mind) a book of my choosing on reasons to doubt faith, and I'd do the same with a book he chose on Christianity.
So the idea here is to pick a book that's the "best argument from the other side" (as in quote 3 here).
I recommended The God Delusion - I'm not sure if that's the best choice given the above intent, but it's what came to mind on the spot.
Would you make a different choice? If so, what?