I consider Greg Bear one of the finest SF writers on the periphery of the genre. I say on the periphery because many of his books transcend SF into a realm I categorize as Relevant Fiction. Greg Bear often mixes truly "on-the-edge" science speculation with politics, society, and three-dimensional characters in such a way as to produce something that is greater than the sum of its parts. Many of his books have an appeal beyond the genre of science fiction.