Mann’s first novel, The Men From the Boys, was published by Dutton in 1997. He continued with a series of novels set in Provincetown, although he has also set his fiction in Palm Springs and Los Angeles. In addition, Mann has written the nonfiction books Wisecracker (1998), a biography of film star William Haines, for which he won the Lambda Literary Award, Behind the Screen: How Gays and Lesbians Shaped Hollywood (2001), Edge of Midnight: The Life of John Schlesinger (2005).

His 2006 biography of Katharine Hepburn, Kate: The Woman Who Was Hepburn, was named one of the Best Books of the Year by Publishers Weekly.  In 2009, Mann wrote How to Be a Movie Star: Elizabeth Taylor in Hollywood. “Reading this life is like gorging on a chocolate sundae,” Publishers Weekly wrote of the book.”This is a smart book about a surprisingly savvy superstar. It’s one of the best Hollywood biographies I’ve ever read,” said Ed Sikov, author of Dark Victory: The Life of Bette Davis.

Hello Gorgeous: Becoming Barbra Streisand (Houghton Mifflin) followed in 2012. “Trying to figure out the Barbra Streisand mystique is no easy task, but Mann expertly captures the launch of her remarkable career in the early 1960s when a unique ‘star was born.’ Mann’s meticulous research and insightful analysis go deeper than any previous biography…” said USA Today.

Tinseltown: Madness, Morphine and Murder at the Dawn of the Movies (HarperCollins, 2014), is the story of how the Hollywood studio system and the Hays Office were established during the early 1920s, told alongside the famous, unsolved murder mystery of director William Desmond Taylor, which Mann solves. Tinseltown was a New York Times bestseller and won the 2015 Edgar Award (presented by the Mystery Writers of America) as Best Fact Crime Book of the Year. NPR named it one of the best books of the year, adding “Brings the early days of the movie industry to sparkling life.” Rex Reed raved: “Sex! Drama! Scandal! If you have the slightest curiosity about the dark purple scars of Hollywood history, this is the go-to book you cannot miss. . . Epic and fabulous—every page is haunting, every chapter a film noir. I was up all night.”