Sci-fi Writers Guild Forum

Hmm, Frank Herbert is truly a good writer. His books other than Dune are hard to find, but they're all worth reading (especially The White Plague.) Also, anything by Arthur C. Clarke, Isaac Asimov, and Robert A. Heinlein is guaranteed to be good. The Gods Themselves by Asimov is one of my favorite books. If you like your science fiction hard and full of real science, Darwin's Radio by Greg Bear is a good one. Brain Wave by Poul Anderson is one of the most thought-provoking books I've read. Michael Crichton's books tend to be thrilling and scientific (and awesome), so if you're in the mood for something that keeps you up at night because you just can't stop reading, one of his books might be a good choice.

Of course, you could always read Dune again. It's well worth it.

I hope some of those help you. I could go on and on about books I enjoyed, but from what you said, I think those are the ones you'll enjoy the most. If they're not your thing, that's perfectly fine, too. I'm sure you can find someone else with similar taste to you.