Tales of Riverworld (1992) (with Philip José Farmer, Martin H Greenberg and Edward E Kramer)
Grails: Quests, Visitations and Other Occurrences (1992)
Confederacy of the Dead (1993) (with Martin H Greenberg and Edward E Kramer)
Quest to Riverworld (1993) (with Philip José Farmer, Martin H Greenberg and Edward E Kramer)
Phobias (1994) (with Wendy Webb)
Excalibur (1995) (with Martin H Greenberg and Edward E Kramer)
The Book of Kings (1995) (with Martin H Greenberg)
More Phobias (1995) (with Martin H Greenberg, Edward E Kramer and Wendy Webb)
Ancient Enchantresses (1995) (with Martin H Greenberg and Kathleen M Massie-Ferch)
Phantoms of the Night (1996) (with Martin H Greenberg)
Grails : Quests of the Dawn (2004) (with Martin H Greenberg and Edward E Kramer)