Throughout his years with the magazine, Boucher was involved in many other projects. He wrote fiction for the SF and mystery markets (primarily short stories). He taught an informal writing class from his home in Berkeley. He continued his Sunday mystery columns for the "New York Times Book Review", while also writing crime-fiction reviews for "The New York Herald Tribune" as Holmes (he also reviewed SF and fantasy (as H. H. Holmes) for the "Herald Tribune") and functioning as chief critic for "Ellery Queen's Mystery Magazine". He edited "True Crime Detective", supervised the Mercury Mystery Line and (later) the Dell Great Mystery Library; hosted "Golden Voices", his series of historical opera recordings for Pacifica Radio, and served (in 1951) as president of Mystery Writers of America.