Hmm...for Sci-Fi I'd suggest Alfred Bester's "The Stars, My Destination"(alternatively called "Tiger, Tiger."), a great relatively short book that has a Monte Cristo feel, but has a wonderful use of suspense and non-described action(sounds weird, but I love it

), and also at one point becomes a calligramme.
You could also try Matheson's "I Am Legend", which is almost completely different to that thing they call a film. A great feeling of solitude and pain, righteous anger and has one of the best "so what is truly evil?" turn arounds I've ever read.
I'd also suggest any sci-fi book by Stanislaw Lem. They're slow and ponderous, but they create a wonderful sense of unease.
And of course there's Isaac Asimov, who's foundation series I just love, and if you enjoyed Herbert's Dune, I think you'll like the Foundation series as well.
For fantasy, I could suggest Scarnight(can't remember the authors name), dark fantasy with really psychotic action sequences.
Terry Brooks' Shannara series is also good as a pretty classic but well written fantasy story, but I wouldn't go past the first trilogy (Sword of Shannara, Elfstones of Shannara, and Wishsong of Shannara), after that he kinda goes loopy.
David Farland's Runelord series is also fun, although that's mainly because of the intriguing "endowment" magic system.
Oooh! And I shouldn't forget anything by H.P. Lovecraft ; gothic cosmic horror fantasy

greatest genre description ever.