Hamill has also written fiction, producing ten novels and two collections of short stories. His first novel, a thriller called A Killing for Christ, about a plot to assassinate the Pope on Easter Sunday in Rome, was published in 1968. Drawing on his youth in Brooklyn he next wrote a semi-autobiographical novel called The Gift. Most of his fiction is set in New York City, including Snow in August (1997), Forever (2003), North River (2007), and Tabloid City (2011).
Hamill has published more than 100 short stories in newspapers, including those that were part of a series called The Eight Million in the New York Post; in the Daily News, his stories ran under the title Tales of New York. He has published two volumes of short stories: The Invisible City: A New York Sketchbook (1980) and Tokyo Sketches (1992).