Of course, the Dune saga. What more could you ask for in a sci-fi =).
Historical fiction, Jack Whyte, hands down. The A Dream of Eagles series is excellent. Probably in my must-reads.
If I'm feeling a little more... deep, I'll pick up Walden by David Henry Thoreau, which is excellent. Great stuff.
Or, As aforementioned, Screwtape Letters by CS Lewis, Velvet Elvis by Rob Bell, and Jesus for President by Shane Claiborne. Excellent reads, and interesting ideas, even if you don't agree with them.
