Hamill's 1994 memoir, A Drinking Life, chronicled his journey from childhood into his thirties, his embrace of drinking and the decision to abandon it. According to Hamill, Frank McCourt was inspired by the book to complete his own memoir, Angela's Ashes. Hamill's memoir Downtown: My Manhattan includes his reporting for the New York Daily News on the destruction of the World Trade Center on September 11, 2001, at which he was present.
His book on the Mexican muralist Diego Rivera was inspired by time spent in Mexico City in 1957 and his presence at Rivera's funeral. In Tools as Art (1995), Hamill surveys the Hechinger Collection and the incorporation of utilitarian objects for aesthetic ends. His biographical essay on the artist was featured in Underground Together: The Art and Life of Harvey Dinnerstein (2008), whose work, like Hamill's, often focuses on the people and cultural life of Brooklyn.
Hamill's interest in photography has informed recent essays in nonfiction. New York: City of Islands (2007), celebrates the photography of Jake Rajs. New York Exposed: Photographs from the Daily News (2001) contains an extended essay about the New York Daily News and its role in American photojournalism. In his introduction to Mexico: The Revolution and Beyond (2003), Hamill writes about Agustin Victor Casasola, whose photographs recorded the Revolution of 1910–1920. In his introduction to A Living Lens: Photographs of Jewish Life from the Pages of the Forward (2007), Hamill evokes the heyday of American Yiddish journalism. His text for The Times Square Gym (1996) enhances John Goodman's photographs of prizefighters, and his introduction to Garden of Dreams: Madison Square Garden (2004) offers a context for the sports photography of George Kalinski. Hamill's Irish heritage informs the text for The Irish Face in America (2004), as seen by the photographer Jim Smith.
Hamill has also written about comic strips, of which he is a collector. Among his writings on the subject are an introduction to Terry and the Pirates: Volume Two by Milton Caniff (2007), and an introductory text for a revised version of Al Hirschfeld's The Speakeasies of 1932 (2003). He also contributed an introduction to Jerry Robinson: Ambassador of Comics (2010).