An American writer who published over thirty works of science fiction and fantasy, he is best known for novels such as A Funeral for the Eyes of Fire; Stolen Faces; Transfigurations; and Under Heaven's Bridge. His later works include No Enemy but Time, Ancient of Days, and Unicorn Mountain.
After graduating from the University of Georgia, he worked as a freelance writer and a substitute teacher.
He was a two-time recipient of the Nebula Award: The Quickening and No Enemy But Time both won the prestigious honor.
He married Jeri Ellis Whitaker in 1969.
He wrote an introduction to a book by Mary Shelley.