Roger Zelazny is one of the writers I think is very under rated. Every time I read his work I wonder why I’m not reading more of it. In gaming circles, one of his most famous works is the Chronicles of Amber which is the nine novels he wrote in the Amber universe. It was later put into game form as Amber Diceless Role-Playing, a game that many designers cite as being formative in their thinking about games.
One I’ve read more recently is Lord of Light which features a group of people in the far future who have effectively become gods by use of technology and decided to call themselves by the names of the Hindu gods. The structure and language of the story is more like a mythic tale than a novel and its delightful reading. I highly recommend picking up anything you can by Mr. Zelazny.