Just a really quick one today, in which I steal content from elsewhere. I posted a little over a month ago about NPR's Top 100 Science-Fiction and Fantasy Books. The folks over at SF Signal have quite rightly pointed out that the list is long, consists of books that vary greatly in style and content, and doesn't come with a handy guide.
So, T. N. Tobias has prepared a nifty flowchart to help you find the sort of book you're looking for. Shrunk down really small, it looks like this:
Useful, no? Even if you've read most of the books on the list, it's always interesting to see how someone else chooses to sub-divide books. For example, I'm not sure I would have defined Iain M. Banks' Culture series by its humour. My favourite book in that series, Use of Weapons, was actually pretty grim.
Also: people seem to like their Military SF!