| Title | Original Publication Year | |-------|--------------------------| | The Mysterious Affair at Styles (Poirot’s first case) | 1920 | | The Secret Adversary (Tommy & Tuppence) | 1922 | | Murder on the Links | 1923 | | The Man in the Brown Suit | 1924 | | The Secret of Chimneys | 1925 | | The Murder of Roger Ackroyd (her breakthrough classic) | 1926 | | The Big Four | 1927 | | The Mystery of the Blue Train | 1928 | | The Seven Dials Mystery | 1929 (Check status: U.S. copyright for 1929 works ends Jan. 1, 2025) |