Diary of a Drug Fiend was Aleister Crowley's first published novel, and is also reportedly the earliest known reference to the Abbey of Thelema in Sicily. The story is widely thought to be based upon Crowley's own drug experiences, despite being written as a fiction. This seems almost conclusively confirmed by Crowley's statement in the novel's preface: "This is a true story. It has been rewritten only so far as was necessary to conceal personalities."

Aleister Crowley (1875 – 1947) was an English occultist, ceremonial magician, poet, painter, novelist, and mountaineer. He founded the religion of Thelema, identifying himself as the prophet entrusted with guiding humanity into the Æon of Horus in the early 20th century.