Haggin wrote twelve books on music and two on ballet. He was the author of the first general guide to recorded classical music, "Music on Records" (1938), later expanded as "The Listener's Musical Companion" (1956), which Haggin regularly updated in new editions until 1978. His best-known books are about Toscanini: "Conversations with Toscanini" (1959), a personal reminiscence and the closest thing to a series of interviews with the publicity-shy Toscanini that has ever been published, and "The Toscanini Musicians Knew" (1967), a series of interviews with musicians who played or sang under the venerable Italian maestro. The two volumes were republished in 1989 as "Arturo Toscanini, Contemporary Recollections of the Maestro".