Maybe I can help a bit too?
If you want fiction, he wrote a planetary series that I have read twice and just think are brilliant (I love Lewis' style). There are 3 of them, and they are actually rather quick reads, except for the last one which gets a bit heavy at times. They are about the inter-planetary travels (and the results) of a man named Ransom who is a linguist and a walker (he loves to take walking trips across England). He stumbles upon a couple of men who are making experiments on planetary travel, and it all starts there....Great books!
Lewis also wrote a TON of non-fiction: God in the Docks; Mere Christianity; Surprised by Joy (I think?) are a few of them, though I could be wrong, please check my resources anyone who cares to. His philosophy & theology are great to read, and I love the man's heart and mind as much as I do Tolkien's. Check him out! Also check out this website, there is a TON of info on it (and a forum like there is here on the Downs):
cslewis.drzeus.net
[ December 03, 2002: Message edited by: Kiara ]