1. Dune by Frank Herbert - one of The Classic Science Fiction books
2. Guns Germs and Steel by Jared Diamond - non-fiction, Jared Diamond's theories about how civilizations are formed.
3. Ghost by John Ringo - This gets filed either under sci/fi, as that's where the author usually gets filed or general fiction, where it really belongs. Somewhere along the lines of James Bond or Mack Boland but not as nice (ok, not nice at all).
4. Foreigner by C. J. Cherryh - Science Fiction, really alien aliens. It'll make your head hurt, but I think it's interesting to have someone write about aliens that really are alien, rather than some flavor or aspect of humanity.
5. Storm Front by Jim Butcher - First book of the Dresden Files, Wizard/Private Eye, fun read, too short.
I'll probably add Amazon links for most of these over time, and I may expand the list. I've got all of these, some in ebook as well, drop me a line if you're interested in borrowing one.