The Mysterious Affair at Styles is a detective novel by Agatha Christie, which was written in the middle of World War I, in 1916. It was Christie’s first published novel, introducing Hercule Poirot, Inspector (later, Chief Inspector) Japp, and Arthur Hastings (Lieutenant and later, Captain).
The story is told in first person by Hastings and features many of the elements that have become icons of the Golden Age of Detective Fiction, largely due to Christie’s influence. It is set in a large, isolated country manor. There are a half-dozen suspects, most of whom are hiding facts about themselves. The book includes maps of the house, the murder scene, and a drawing of a fragment of a will, as well as a number of red herrings and surprise plot twists.