He also wrote under the pseudonyms of Geoffrey Marsh, Lionel Fenn, Simon Lake, Felicia Andrews, Deborah Lewis, Timothy Boggs, Mark Rivers, and Steven Charles.

Then, from 1968 to 1970, Grant served in the U.S. Army military police in Vietnam and was awarded a Bronze Star.

His story "Temperature Days on Hawthorne Street" was adapted into an episode of Tales from the Darkside titled "The Milkman Cometh" in 1987, the same year he wrote the Introduction and Afterward to Tor Books' publication of Washington Irving's The Legend of Sleepy Hollow, Grant's favorite Irving story.

[4] Grant wrote twelve books (eight novels and four collections of four related novellas each, with interstitial material) set in the fictional Connecticut town of Oxrun Station.

Three of these were intentionally pastiches of classic Universal and Hammer horror films, and feature a vampire, a werewolf, and an animated mummy.