The Poisonwood Bible melds an adventure story, conceivable to any of us, with soul-piercing observations on the human condition. If you haven't; read it. If you have; read it again. It's worth it.
I read it first about 8 years ago, and have listened to it twice on CD recently. A good CD book combines a good narrator with a good story, and none are better in combination than Poisonwood Bible read by Dean Robertson.
I read lots of books I hate to see end, but I know I'll find another that will make me feel that way. Poisonwood, however, is a singular event in my reading of books.