Canadian author of more than 30 novels with a wide range of appeal, particularly noted for his wit and humour.

While a student at Acadia College (now Acadia University, Wolfville, Nova Scotia), De Mille traveled extensively in Europe, and scenes of Italy became settings for many of his novels. After an unsuccessful venture as a bookseller, De Mille became a professor of classics at Acadia College (1860–64) and then of English at Dalhousie University in Halifax (1864–80). De Mille's popular fiction for adults included thrillers, such as The Cryptogram (1871); comic novels of adventure, such as The Dodge Club; or, Italy in 1859 (1869); and historical romances, such as A Tale of Rome in the First Century (1867). Writings for young readers included the “B.O.W.C.” (“Brethren of the White Cross”) series, the first popular boys' adventure stories produced in Canada. De Mille's imagination ranged furthest in A Strange Manuscript Found in a Copper Cylinder (1888), a fantasy travel narrative that satirizes Western notions of progress through an account of the imaginary society of the Kosekin in Antarctica.