Autumnworld Mosaic

• The Alchemists (1984; nominated for Philip K. Dick Award for best novel)
• The Pathfinders (1986) (sequel to Alchemists)

War of the Fading Worlds

• A Key for the Nonesuch (1990)
• Return of the Breakneck Boys (1991) (sequel to Nonesuch)

Hook

• Hook: A Novel for Young Readers (1992) (novelization based on the Steven Spielberg Motion Picture)

Batman

• Mask of the Phantasm (1993) (novelization based on Batman: Mask of the Phantasm)
• Shadows of the Past (1993) (novelization based on Batman: The Animated Series)
• Dual to the Death (1994) (Batman: The Animated Series)
• The Dragon and the Bat (1994) (Batman: The Animated Series)
• Batman and Mr. Freeze (1997) (A Golden Book)

Might and Magic

• The Dreamwright (1995) (a Might and Magic novel)
• The Shadowsmith (1996) (sequel to Dreamwright)

Edgar Rice Burroughs Universe

• John Carter of Mars: Gods of the Forgotten (2021) (authorized sequel to the Mars series of Edgar Rice Burroughs)

• Geary Gravel at the Internet Speculative Fiction Database
• Geary Gravel at the SF Encyclopedia