* The City Between (1987)
* Shadow of Obsession (1990)
* The Sixth Sun (1991)
* Resurrection Days (1992)
* The Orpheus Legacy (1994)
* Fire Ice (2001)
* The Deepest Darkness (2010)
* The Red Hand (2012)
* Children of the Blood (2014)
* The Devil's Due (2016)
* The Last Witness (2018)
Non-fiction
* The Science of Fiction: A Guide to Writing Science Fiction (1993)
* Writing the Fantastic: A Guide to Writing Fantasy, Horror, and Science Fiction (2001)
* Writer's Guide to the Universe: Building Universes for Fiction, Television, and Games (2008)
* Creating Character Arcs: The Master Tool for Building Story Structure (2013)
* 2200 Tech: A Futurologist's Guide to the Next Fifty Years (2016)