After my post on science fiction, people have ask for some of my favorites. It is very hard to make a list because there is so much great stuff. So here are several recommendations with particular no order.

Enders Game by Orson Scott Card
Hyperion by Dan Simmons
Empire by Orson Scott Card
Ring World by Larry Niven
Atlas Shrugged by Ayn Rand--it's true, this book is not really science fiction per se, but it is in the sense that it predicts and explores a possible future.
The Foundation Trilogy by Isaac Asimov.
Diamond Age by Neil Stephenson

I will think of some more, but these should get you started.