Depends on what type or era you're interested in. Having grown up in the 60s and 70s I have always had a preference for the modern masters; Heinlein, Asimov, Clarke, P.K. Dick, Niven and Bradbury. Some of my favorites are 'The Moon is a Harsh Mistress' and 'Starship Troopers' by Heinlein but forget that movie its about social ethic and civic responsibility. '2001', 'Rendezvous with Rama' or almost anything by Clarke or Asimov is a good read. The first two in Niven's 'Ringworld' series are good but the last was a bit too odd.
Enjoy I know I did.