“I’m a writer who is gay,” the novelist Armistead Maupin says in “The Untold Tales of Armistead Maupin.” “I’m not a gay writer. I write about heterosexuals as well.” This fond documentary portrait, directed by Jennifer M. Kroot, makes it clear that Mr. Maupin’s mastery of assorted perspectives is his gift, evident in his masterpiece, “Tales of the City,” a love letter to San Francisco comprising multiple characters. And yet the film offers an enlightening glimpse into how the gay experience informed Mr. Maupin’s art.

Mr. Maupin, 73, grew up in Raleigh, N.C., the son of a conservative, distant father. To win his approval, he served in Vietnam and even met Richard M. Nixon in the White House. Little did Nixon know that Mr. Maupin would later migrate to San Francisco, come out and encounter a broad variety of men of diverse backgrounds. Such meetings provided the invaluable insight that fed his newspaper serial “Tales of the City,” which grew into a book and eventually a groundbreaking television mini-series.

Friends like Laura Linney, Ian McKellen, Amy Tan and Neil Gaiman testify to Mr. Maupin’s generosity of spirit, while the writer speaks candidly about cruising in Raleigh public parks, Fairmont Hotel trysts with Rock Hudson and the agonies of the AIDS crisis. Now Mr. Maupin is content with a husband, extolling what he calls the “logical family” of his gay peers over the “biological family” of straight society. For all his distinguished man-of-letters status, he is warm and winning company.