TRENT'S LAST CASE (Detective Novel). E. C. Bentley

Detective Philip Trent investigates the mysterious murder of a leading financier. Despite the title, Trent's Last Case is the first novel in which the gentleman sleuth Philip Trent appears. The novel is a whodunit with a place in detective fiction history because it is the first major sendup of that genre: Not only does Trent fall in love with one of the primary suspects—usually considered a no-no—he also, after painstakingly collecting all the evidence, draws all the wrong conclusions! This novel was much praised, numbering Dorothy L. Sayers among its admirers, and with its labyrinthine and mystifying plotting can be seen as the first truly modern mystery. It was adapted as a film in 1920, 1929, and 1952. The success of the work inspired him, after 23 years, to write a sequel, Trent's Own Case.