Logical Magician
1. A Logical Magician (1994)
     aka A Modern Magician
2. A Calculated Magic (1995)

Masquerade of the Red Death
1. Bloodwar: Masquerade of the Red Death (1995)
2. Unholy Allies (1995)
3. The Unbeholden (1996)

Horizon War
1. The Road to Hell (1996)
2. The Ascension Warrior (1997)
3. War in Heaven (1998)

The Termination Node (1999) (with Lois Gresh)
Dark Earth: The Torch (1999)
City of Heroes: The Web of Arachnos (2005)
The Adventure of the Parisian Gentleman (2012) (with Lois Gresh)

When The Night Comes Down (2010) (with Joseph D'Lacey, Nate Kenyon and Bev Vincent)

Star Trek : The Original Series (with Lois Gresh)
The Computers of Star Trek (1999)

Kolchak: The Night Stalker (with Elaine Bergstrom, Max Allan Collins, Peter David, Mark Dawidziak, P N Elrod, Ed Gorman, C J Henderson, Stuart M Kaminsky and Brett Matthews)
The Night Stalker Chronicles (2005)

James Bond (with Lois Gresh)
The Science of James Bond (2006)

Dr Satan: Pulp Classics 6 (1974)
Revelry in Hell: Pulp Classics 3 (1974)
Far Below and Other Horrors (1974)
Devils in the Dark (1979)
100 Tiny Terror Tales (1984) (with Stefan R Dziemianowicz and Martin H Greenberg)
The Eighth Green Man and Other Strange Folk (1987)
Weird Tales: 32 Unearthed Horrors (1988) (with Stefan R Dziemianowicz and Martin H Greenberg)
The Mists From Beyond: 22 Ghost Stories and Tales from the Other Side (1989) (with Stefan R Dziemianowicz and Martin H Greenberg)
Between Time and Terror (1990) (with Stefan R Dziemianowicz and Martin H Greenberg)
Rivals of Weird Tales (1990) (with Stefan R Dziemianowicz and Martin H Greenberg)
100 Fiendish Little Frightmares (1990) (with Stefan R Dziemianowicz and Martin H Greenberg)
Lovecraft's Legacy (1990) (with Martin H Greenberg)
Famous Fantastic Mysteries (1991) (with Stefan R Dziemianowicz and Martin H Greenberg)
Hard-Boiled Detectives: 23 Great Stories from Dime Detective Magazine (1992) (with Stefan R Dziemianowicz)
100 Ghastly Little Ghost Stories (1992) (with Stefan R Dziemianowicz and Martin H Greenberg)
Weird Vampire Tales (1992) (with Stefan R Dziemianowicz and Martin H Greenberg)
A Taste for Blood (1992) (with Stefan R Dziemianowicz and Martin H Greenberg)
Nursery Crimes (1993) (with Stefan R Dziemianowicz and Martin H Greenberg)
100 Dastardly Little Detective Stories (1993) (with Stefan R Dziemianowicz and Martin H Greenberg)
To Sleep, Perchance to Dream...Nightmare (1993) (with Stefan R Dziemianowicz and Martin H Greenberg)
Tough Guys and Dangerous Dames (1993)
100 Crooked Little Crime Stories (1994) (with Stefan R Dziemianowicz and Martin H Greenberg)
100 Creepy Little Creature Stories (1994) (with Stefan R Dziemianowicz and Martin H Greenberg)
100 Wild Little Weird Tales (1994) (with Stefan R Dziemianowicz and Martin H Greenberg)
100 Wicked Little Witch Stories (1995) (with Stefan R Dziemianowicz and Martin H Greenberg)
Great Writers and Kids Write Spooky Stories (1995) (with Martin H Greenberg and Jill M Morgan)
100 Vicious Little Vampire Stories (1995) (with Stefan R Dziemianowicz and Martin H Greenberg)
Virtuous Vampires (1996) (with Stefan R Dziemianowicz and Martin H Greenberg)
100 Astounding Little Alien Stories (1996) (with Stefan R Dziemianowicz and Martin H Greenberg)
100 Tiny Tales of Terror (1996) (with Stefan R Dziemianowicz and Martin H Greenberg)
Miskatonic University (1996) (with Martin H Greenberg)
Rivals of Dracula (1996) (with Stefan R Dziemianowicz and Martin H Greenberg)
Girls' Night Out: 29 Female Vampire Stories (1997) (with Stefan R Dziemianowicz and Martin H Greenberg)
Mistresses of the Dark: 25 Macabre Tales by Master Storytellers (1998) (with Stefan R Dziemianowicz and Denise Little)
100 Twisted Little Tales of Torment (1998) (with Stefan R Dziemianowicz and Martin H Greenberg)
100 Hilarious Little Howlers (1999) (with Stefan R Dziemianowicz and Martin H Greenberg)
Dial Your Dreams: And Other Nightmares (2001)
H.P. Lovecraft's Cthulhu Mythos: A Weird Tales Retrospective (2011) (with John Gregory Betancourt)

The Annotated Guide to Robert E. Howard's Sword and Sorcery (1976) (see Robert E Howard)
The Weird Tales Story (1977)
A Biographical Dictionary of Science Fiction and Fantasy Artists (1988)
Horror of the 20th Century (1991)
The Science of Superheroes (2002) (with Lois Gresh)
The Science of Supervillains (2004) (with Lois Gresh)
The Science of Anime: Mecha-Noids and AI-Super-Bots (2005) (with Lois Gresh)
The Science of Stephen King (2007) (with Lois Gresh) (see Stephen King)