Kent Family Chronicles:
The Bastard (1974)
The Rebels (1975)
The Seekers (1975)
The Furies (1976)
The Titans (1976)
The Warriors (1977)
The Lawless (1978)
The Americans (1980)

North and South Trilogy:
North and South (1982)
Love and War (1984)
Heaven and Hell (1988)

Crown Family Saga:
Homeland (1993)
American Dreams (1998)

Brak the Barbarian:
Brak the Barbarian (1968)
Brak the Barbarian Versus the Mark of Demons (1969)
Brak the Barbarian Versus the Sorceress (1969)
Brak: When Idols Walked (1978)
Mark of the Demons (2012)
Witch of the Four Winds/When the Idols Walked (2012)

Johnny Havoc:
Johnny Havoc (1960)
Johnny Havoc Meets Zelda (1962)
Johnny Havoc and the Doll Who Had "It" (1963)
Johnny Havoc and the Siren in Red (1968) - a.k.a. Making It Big

Gavin Black:
Master of the Dark Gate (1970)
Witch of the Dark Gate (1972)

Dragonard Trilogy:
When the Star Kings Die (1967)
The Planet Wizard (1969)
Tonight We Steal the Stars (1969)

Young Adult Novels:
The Texans Ride North (1952)
Secrets of Stardeep (1969)
Time Gate (1972)

Other Books:
Wear a Fast Gun (1956)
A Night for Treason (1956)
The Devil Has Four Faces (1958)
The Imposter (1959)
G.I. Girls (1963)
The Asylum World (1969)
The Hybrid (1969)
The Last Magicians (1969)
Mohawk (1969)
Six Sun Planet (1970)
Mask of Chaos (1970)
Monte Cristo 99 (1970)
Back in Time (1970)
Mention My Name in Atlantis (1972)
On Wheels (1973)
Conquest of the Planet of the Apes (1974)
Kings' Crusader (1977)
Excalibur! (1984)
California Gold (1989)
Homeland (1993)
American Dreams (1998)
The Bold Frontier (2001)
On Secret Service (2001)
Charleston (2002)
Savannah {Or} A Gift For Mr. Lincoln (2004)
The Gods of Newport (2006)