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. It was Christie's first published novel. It introduced Hercule Poirot, Inspector (later, Chief Inspector) Japp, and Arthur Hastings. The true first publication of the novel was as a weekly serial in the The Times. This first mystery novel by Agatha Christie was well received by reviewers.