The Michael Grumley Papers primarily contain his writings and supporting research material, with a small amount of personal correspondence and personal papers. More than half of the collection consists of his creative writings and drawings, spanning his college years through his career as a freelance author, many of which were not published during his lifetime. In addition to his one novel and his four books on the topics of Atlantis, Sasquatch, sadomasochism, and night workers, Grumley wrote columns and criticism for periodicals such as the New York Native and the Philadelphia Gay News. His files hold research notes, contracts, drafts, tear sheets, reviews, and fan mail.
While most of Grumley's writings explored alternative legends and lifestyles, he also composed short works of whimsy for both children and adults. In addition to preparing texts, he drew illustrations for several of his own projects, such as a proposed book on tarot, and created images to accompany other writers' words; also in the collection are more than one hundred of his stylized ink drawings. Equally important are Grumley's set of daily journals and engagement calendars which provide an intimate narrative of the activities, culture, and community of an American writer fully experiencing life in New York, Rome, and London in the 1970s and 1980s, in particular a life lived in the midst of the AIDS epidemic.