Green was born in Bradford, Pennsylvania, in 1944. A resident of Michigan since 1947, he was graduated from Ypsilanti High School in Ypsilanti in 1962. He received a B.A. from Oberlin College in 1966 in Political Science, then moved to Chicago to attend the University of Chicago from which he received an MA in International Politics in 1968. While there, he became active in science fiction fandom and in the Society for Creative Anachronism (under the persona "Roland de Tour Gris"). He married fellow writer Frieda A. Murray in 1975; their one daughter Violette Y. Green was born in 1984.

Green has worked as a full-time writer and reviewer most of the time since he sold his first novel, Wandor's Ride, in 1973. While his earliest published novels were the "Wandor" sword and sorcery series, Green's most prominent works are his military action adventures of the future, including the Starcruiser Shenandoah series, the Peace Company series, and Voyage to Eneh (2003). He has also written a number of Conan novels published by Tor Books and has co-authored several novels as well. He pseudonymously wrote all but one of the Richard Blade series books from number 9 up to the end of the series.

Wandor series

• Wandor's Ride (1973)
• Wandor's Journey (1975)
• Wandor's Voyage (1979)
• Wandor's Flight (1981)

Conan (shared universe)

• Conan the Valiant (1988)
• Conan the Guardian (1991)
• Conan the Relentless (1992)
• Conan and the Gods of the Mountain (1993)
• Conan at the Demon's Gate (1994)
• Conan and the Mists of Doom (1995)
• Conan and the Death Lord of Thanza (1997)

Dragonlance Warriors (shared universe)

• Knights of the Crown (1995)
• Knights of the Sword (1995)
• Knights of the Rose (1996)
• The Wayward Knights (1997)

Peace Company

• Peace Company (1985)
• These Green Foreign Hills (1987)
• The Mountain Walks (1989)

Starcruiser Shenandoah

• Squadron Alert (1989)
• Division of the Spoils (1990)
• The Sum of Things (1991)
• Vain Command (1992)
• The Painful Field (1993)
• Warriors for the Working Day (1994)

Janissaries series

• Clan and Crown (1982) (with Jerry Pournelle)
• Storms of Victory (1987) (with Jerry Pournelle)
• Tran (1996) (with Jerry Pournelle) (omnibus of the two novels above, the second and third in the Janissaries series)

Richard Blade series

Green wrote books 9-29, 31-37 of the Richard Blade series (as by "Jeffrey Lord"). The series was published by Pinnacle Books using the house pseudonym.

Other novels

• Jamie the Red (1984) (with Gordon R. Dickson)
• Assignment - Hellhole (1983) (with Andrew J. Offutt [as by "John Cleve"]) Book 14 in the "Spaceways" series
• The Book of Kantela (1985) (with Frieda A. Murray)
• Great Kings' War (1985) (with John F. Carr) the sequel to Lord Kalvan of Otherwhen by H. Beam Piper
• Fantastic Adventures: The Tale of the Comet (1997)
• On the Verge (1998)
• Voyage to Eneh (2000)

Anthologies

• Women at War (1995) (with Lois McMaster Bujold)
• Alternate Generals (1998) (with Martin H. Greenberg and Harry Turtledove)
• Worlds of Honor (1999) (short story Deck Load Strike)