Gilman enlisted into the U.S. Marine Corps in 1941 and was stationed in the Pacific during World War II.
After converting to Catholicism, he wrote for the left-leaning Catholic journal Commonweal and from 1964 to 1967, he was the drama critic for Newsweek.
[2] In 1966, Gilman married Lynn Nesbit, a literary agent,[2] (who would go on to co-found the literary agency Janklow & Nesbit Associates with Morton L. Janklow), In 1992, Gilman married Japanese scholar, Yasuko Shiojiri, who would translate his books into Japanese.
[2] Gilman died of lung cancer on October 28, 2006, at the age of 83 at his home in Kusatsu, Shiga Prefecture, Japan.
His memoir Faith, Sex, Mystery is primarily devoted to explaining his conversion and deconversion.