Listing all my favourite books would take forever, really, so I'll just mention the ones that aren't so well-known. Micheal Marhall Smith is superb; is it fantasy? Science fiction? A complicated allegory? You don't really find out until the very end. C. S. Lewis doesn't need a plug, but his adult books might. Check out his Cosmic Trilogy. Robin McKinley's Sunshine is a lovely read too - with baking! Donna Tartt's The Secret History is a proper tragedy. China Mieville is another one whose sheer originality blows my mind, every time. It's a huge complicated fantasy world, and it's nothing at all like Middle-Earth!
In the non-fiction category, Chaos by James Gleick is great. If it doesn't take your breath away, you probably weren't paying attention. Or else you really don't like physics
Children's books: I retain a soft spot for E. Nesbit and the Just William stories. And Joan Aiken. And all the usual suspects, of course...
EDIT: I completely forgot to mention Lemony Snicket, Edward Gorey, Alexander McCall Smith, and doubtless many more.
