I have read literally hundreds of books, but I have very few I consider "favorites". I don't think I can make a top 20 list. The first six on this list are certainly favorites for me.
1. Shogun - James Clavell
2. Boy's Life - Robert McCammon
3. Memoirs of a Geisha - Arthur Golden
4. The Poisonwood Bible - Barbara Kingslover
5. Angela's Ashes and/or 'Tis - Frank McCourt
6. Watchmen - Alan Moore
7. Dune - Frank Herbert
8. Speaker for the Dead - Orson Scott Card
9. Different Seasons - Stephen King (for "The Body" and "Rita Hayworth and the Shawshank Redemption")
10. Weaveworld - Clive Barker
Yeah, I'm done. I can't think of anything else. I have been staring at the screen for ages now.