A lifelong resident of New York City, Long was educated in the New York City public school system. As a boy he was fascinated by natural history, and wrote that he dreamed of running "away from home and explore the great rain forests of the Amazon." He developed his interest in the weird by reading the Oz books, Jules Verne, and H.G. Wells as well as Ambrose Bierce and Edgar Allan Poe. Though writing was to be his life's work, he once commented that as "important as writing is, I could have been completely happy if I had a secure position in a field that has always had a tremendous emotion and an imaginative appeal for me—that of natural history."