I remember "The Wall at the Edge of the World" by Jim Aikin and "The Shattered World" by Michael Reaves.
The first novel is about a dystopia set in the future. Mankind consists of a small totalitarian, telepathic, hive-like society. The old world was destroyed by this society and has long since returned to a wild state. However, small groups of ordinary survivors still remain, and when they discover the telepathic society, confict results.
The second novel is a fantasy novel, set in a world that was broken up by magic. I honestly don't remember much of the plot now, but the novel was set in a very original world that I still remember.
There is a good horror/sci-fi/suspense movie here somewhere.
What is algebra, exactly? Is it one of those three-cornered things? -- J.M. Barrie