I just finished reading Pride and Prejudice, it is a personal favorite of mine. A teacher recently commented on how everyone should have a book they read every 10 years or so, ideally one that you have read in childhood, teenage years and so on. The thought behind this is that in a good piece of literature you will find different things as you mature. The example he gave was Huckleberry Finn.
I have given quite a bit of thought to this, the best books I can think of for me are Little House on the Prairie and Anne of Green Gables. I think Pride and Prejudice fits into this category as well though. I first read it in high school (while traveling in England, it was amazing) but even as I read it again this time I noticed things that I hadn't picked up before. Mr. Darcy has a sense of humor! What book can you read over and over?