The Sword and Laser group over on GoodReads has a thread asking for your five favorite SF&F authors. I cheated a bit there and listed ten of my favorite authors from multiple genres.
In no particular order, I listed:
Douglas Preston & Lincoln Child
F. Paul Wilson
E. E. Knight
The first three on the list are action/thriller authors. Asimov and Bova, well, do I even need to explain? F. Paul Wilson is a horror author, but his excellent Repairman Jack series is more thriller/paranormal. E. E. Knight writes both Science Fiction (post-apocalyptic) and Fantasy. Derek and Sharon Gilbert write Christian fiction, and Derek has a great novel about dragons too. And Jack McDevitt has some good SF as well.