The Bible. Seriously, and I really don't mean this as a "religious" post. It's something that I've always wanted to do. To read it from beginning to end, cover to cover, to see if I "get it". So far I'm a little past the half way mark in the Old Testament, or 1/3rd of the way through the whole "project" (as I'm calling it). Pun intended, but it really is a good book. Interesting on many levels, and recommended.
(Fellow mods, you can zap this post if you think it's inappropriate, but I was just honestly answering the question and don't mean in any way to stir up the pot or to get a religious discussion started. In fact, if you read it the way I am, for the stories involved, it really is just a book... sort of).
Also, "East of Eden" by John Steinback.