This one is a little tougher - I've read quite a bit of it and a lot of it is not that great.
I'm going to pick an author who wrote two different series of books that now have RPG's: William King. He wrote the first set of Gotrek and Felix books set in the Old World of Warhammer Fantasy, and the original set of Space Wolf novels in the Warhammer 40,000 universe. To me they felt a cut above most of what's out there in gaming-fiction-land. They have a very old school, pulp feel, more like the Conan or Fafhrd/Grey Mouser books than the newer style of setting novels. They are far more gritty than they are sweeping epic of high fantasy or space opera.