That debate helped me understand my own favorites. My favorite books are completely different from the ones I might list should people ask me, "What would you recommend?" When someone asks about my favorites, I think back to books I have read more than once; books that have become important to me for a variety of reasons. As an example, I will not recommend Hitchhiker's Guide to the Galaxy to a person who is not at all interested in silly sci-fi humor, although it's a book (series?) I grew up reading and re-reading, chatting with my old friends about it and making new friends over it. Later in college, it became the please take me to a happy place book I had to read every ten or twenty pages of horror I was subjected to in the Wasp Factory. I have a hard copy of the collection, but I bought a Kindle edition as well in case I need a bit of cheering up on the road, wherever I am.
Add to that the brain space the books I've read most recently are taking up: I was tempted to just list the ones that had impressed me in recent years, right about the time when my reading habits had dramatically shifted (this seems to happen to me every 5 years or so). And all these nonfiction books kept on wanting to creep in!
Here are mine, in no particular order, and while typing most of them I thought, "Man, I need to read that again..." Except LOTR. I've read it so many times that I do not have any immediate need to read it again.
1. Middlesex by Jeffrey Eugenides
2. Flowers for Algernon by Daniel Keyes
3. The Lord of the Rings by J.R.R. Tolkien
4. The Hitchhiker's Guide to the Galaxy by Douglas Adams
5. Diamond Age, or a Young Lady's Illustrated Primer by Neal Stephenson (although... the older I get, the more I like Cryptonomicon. It's like a Skywalker vs Solo kind of a thing)
6. The World According to Garp by John Irving
7. American Girl by Monika Fagerholm
8. Vihreä tukka by Aila Meriluoto
9. The House of Leaves by Mark Z. Danielewski
10. The Blind Assassin by Margaret Atwood
The more I look at this list, the more doubtful I'm of some of them... Maybe I don't have "favorites" at all; just books I really like when I'm in a certain mood.
Riikka Pulkkinen's True and Peter Watts's Blindsight almost made it to the list: I loved every single sentence in these extremely different books and I can see rereading them both over and over--but it's too soon to call them favorites. I'll need to wait for the initial infatuation to die down.
Quite frankly, this is the main reason why almost all of the books I have listed aren't anything I've read within the past two years. I just finished that Steve-O biography and right now, I feel like it's among my favorite nonfiction books ever--but will I feel that way in two months? We'll see.
EDIT: I cannot believe I completely and utterly forgot the book that I always tell people is one of my favorites: The Speaker for the Dead by Orson Scott Card. See!