The first that springs to mind is The Space Trilogy. There's actually a discussion thread comparing the two here, that might be interesting (and might have a few spoilers, so...tread with care?). Then there's the Screwtape Letters, which is probably a good bridge from his fiction to theological writings, The Pilgrim's Regress (as opposed to Pilgrim's Progress), Till We Have Faces, which is Greek mythology based, and The Great Divorce, which has a vague Divine Comedy air to it.

I'm sure there are more, but that should give you a good idea of some starter points! Just as a heads up, at least to me, all of these books strike me as having a very different flavor from Narnia, perhaps because they really are written for adults, not for children and adults.

Wow, that is interesting stuff! Thanks for the info.

It's funny you mention Pilgrim's Progress (which is another one I want to read) - my dad thought he wrote it, but then I Ducked it and found out it was written in like the 17th century. I had a good laugh about that, thinking, "what gave him that crazy idea?" But if he wrote a story called The Pilgrim's REgress, I finally understand where he got that from.

And I was SURE I heard about a space trilogy somewhere - it just sounded more Lucas than Lewis to me. I mean, they didn't get to the moon until 1969, so I was starting to wonder if that was just a rumor. I'm definitely going to look for that (before I check out that thread - thanks for the spoiler warning lol).

Anyway, I'm kind of glad I didn't read these others yet. If I had read them as a kid, I probably wouldn't have appreciated them as much. But reading them as an adult, and more importantly as a Christian, I'm sure they'll be interesting to say the least.

My favorite fictional book by C. S. Lewis apart from The Chronicles of Narnia and The Screwtape Letters is Till We Have Faces which is actually a bit surprising. While I'd heard the book praised, I didn't have high expectations of it because I'm tired of stories where they take a famous story and make the villain the hero and vice versa. Not that it's intrinsically a bad idea but everybody does it and it's not really provocative anymore. If people want to do an original twist on a familiar story, I think they should find one that's actually...original. Till We Have Faces is so awesome though that I feel it transcends its subgenre.

The most famous nonfiction work of Lewis' which I've read is Mere Christianity and I'm not sure how to evaluate. I feel like the only way to really tell if a work of apologetics is good is to read counterarguments to it and then read counterarguments to those counterarguments and then read counterarguments to those counterarguments...and by then you have a headache and you can't remember what you were reading in the first place. FWIW though I thought the book seemed mostly sensible.

I've heard someone say though that Lewis was responding Modernism and his arguments wouldn't be of as much weight to someone with a Postmodern mindset. (The person I heard say this was a fan of Lewis BTW, not a detractor.) It's probably good to keep that in mind when considering the book as an apologetics resource. I guess my mindset is more Modern than Postmodern because, like I said, it made sense to me.

P.S.
I wrote about the reading The last book in The Space Trilogy in the Books thread
(But don't read the spoilered part if you don't want to hear about the climax.)

Hello everyone,

Apart from Narnia, I've read and greatly appreciated The Screwtape Letters. I did also read Out of the Silent Planet a few years ago, but I'm sorry to say I didn't enjoy it at all in the end (although the chapters where Ransom is living with the hrossa were very good and moving). I know many other Christians love the Space Trilogy and I was expecting to enjoy it too, so that was a big disappointment. But each to their own and I certainly didn't think any less of Lewis for it! I do think his writing style — his ability to paint a scene with the most concise and effective words — really improved over the years between the Space Trilogy and the Narnia Chronicles. Possibly because by 1950 he'd had a lot more experience in talking to different audiences about matters of faith in ways that ordinary people could understand and relate to.

On that note, I've read about half of Mere Christianity and greatly appreciated it, but for some reason I put it aside and have never got through the rest of it. Not because I found it difficult (it's a great read!), but I think just because I had a lot of other things to do at the time. I will get back to it at some stage. I can see why it's a classic of Christian apologetics — and all the more compelling when you remember the circumstances under which it was originally written and presented. This paragraph (one of my favourites) is striking enough even now:

Enemy-occupied territory — that is what this world is. Christianity is the story of how the rightful king has landed, you might say landed in disguise, and is calling us all to take part in a great campaign of sabotage. When you go to church you are really listening-in to the secret wireless from our friends; that is why the enemy is so anxious to prevent us from going.

And then when you remember this was originally broadcast on BBC Radio in 1942, it suddenly hits you in the gut as you realise — his original audience knew EXACTLY what he was talking about.

I'd also be very interested to read Till We Have Faces — am I right in thinking it was Lewis's own favourite among his works? — and a couple of others I'm aware of that sound like they'd be very good to try: The Great Divorce and The Pilgrim's Regress. I'm aware the latter is Lewis's first work on Christianity and is sometimes described as "difficult", but I gather it works through a lot of his own initial objections to the faith and how they were resolved — which is a point of interest to me as someone who also came to Christianity as an adult from an agnostic (never quite atheist) background.

Has anyone else here read those particular books? If so, I'd love to hear your thoughts on them. (No plot spoilers if you can help it, please! )

Take what I say with a grain of salt, as I liked a great deal of The Space Trilogy so obviously our tastes are different. But. 

Till We Have Faces, to my mind, was gorgeous. It was very dark at times, but I appreciated the struggles of the well-rounded FMC, and the way we work through her anger and fears with her until we come to a kind of... revelation of theodicy, although in a pagan setting. 

The Great Divorce, I am still processing. It has a few really jewel-bright bits though, and a great deal that makes me think, even if I am not sure how I feel about it.