The Mysterious Affair at Styles is a detective novel by Agatha Christie. It was written in the middle of the First World War, in 1916, and first published by John Lane in the United States in October 1920 and in the United Kingdom by The Bodley Head (John Lane's UK company) on 21 January 1921. The US edition retailed at $2.00 and the UK edition at seven shillings and sixpence (7/6).