Holy Genre Jumper's Batman, It's Dan Simmons!
There are many authors who write in multiple genres, but one of my personal favorites is Dan Simmons. I haven't been disapointed by any of his titles yet. Three of my favorites:
Summer of Night. Something evil is haunting a small Illinois town. Only the children know, and they must find a way to defeat it. Sure, it sounds like Stephen King's It, but once you get into this one you really won't care.
In Science Fiction:
Hyperion. Winner of the 1990 Hugo Award. This novel takes a look at 7 pilgrims who are on their way to Hyperion, a remote planet inhabited by the mysterious shrike, a fearsome metal thorned creature. Ostensibly the pilgrims are going to find answers to help bring peace to a universe on the brink of war, but each of them has their own mysterious reasons for wanting to visit Hyperion. You will want to get the sequel, the Fall of Hyperion right away, because there is no closure at the end of Hyperion, just a great big cliff hanger.
Darwin's Blade. Accident investigator doesn’t sound like an occupation that an action hero should have, but Dr. Darwin Minor fills both roles nicely. An investigation into insurance fraud leads Darwin to butt heads with powerful celebrities and the Russian mob. Darwin's Blade is written very much tongue in cheek, (some of the accidents that Darwin investigates are taken from urban legends) but the suspense and action are top notch.