As usual, fiction books run a second to non-fiction, and also to older fiction. I could easily say that the best novel I read this year was A Wizard of Earthsea, but you'd consider me cheating, and rightly so --- the book was published in the 1960s, but if you haven't read it, please do. I think it's amazingly well-written and stands up to time --- the human condition certainly doesn't change much, so enduringly good fiction is still great.
The best new novel I read this year was Adiamante, for its exploration of important issues and a critique of the military approach to problem solving. But that's closely followed by runners up The Dragons of Babel and The Atrocity Archives, both excellent novels and very much worth your time. I would also be remiss if I didn't mention Richard Morgan as the best new-to-me author of the year. I'm working through Thirteen right now, and it's great reading, as much fun as Altered Carbon. It's so great to see an author continually produce great work, since it means there's more great reading to come. Tim Power's Declare also deserves an honorable mention.
Finally, let me plug the Kindle one more time --- it truly is the first interesting improvement to the reading experience, and I like it more and more, especially when comparing it to paper-books. If you are a serious reader (of books that are mostly words), you owe it to yourself to get one. Forget the rumors of the 2.0 version, just get it. It's just about doubled my reading rate, and has paid for itself several times over.