A little research also confirmed my theory. Raymond E. Feist had a D&D group that met weekly. I can only imagine that the characters I'm reading about were played by people around the table, and the stories (which are pretty great) were probably adventures that they went on as a group. As I'm reading, I think to myself, "Okay that is the rogue in the party, definitely the magic-user, who's the tank? Oh...that's this one."
Anyway, about the only thing I can compare them to are the Dragonlance novels by Tracy Hickman and Margaret Weiss. Those (intentionally) read as a Dungeons & Dragons game group, because they were written for Dungeons & Dragons. So that really was the whole purpose behind their creation. I just think that it's interesting how influential a silly game like D&D is on an entire genre. I suppose that D&D originally pulled its inspiration from the works of Tolkien, C.S. Lewis, and Lloyd Alexander. And now it's influence inspires other authors to write, because they fall in love with the characters they've created (and the stories they put those characters through over the years).
So I have this question for my few readers: Have you ever created a D&D character or a character in another RPG system that inspired you to write stories about them? If so, please share. I'd like to hear about it.