Agatha Christie was born Agatha Mary Clarissa Miller on September 5, 1890, in Torquay, England. In 1914 she married Colonel Archibald Christie, an aviator in the Royal Flying Corps. They had a daughter, Rosalind, and divorced in 1928. By that time, Christie had begun writing mystery stories, initially in response to a dare from her sister. Her first novel, The Mysterious Affair at Styles, was published in 1920 and featured the debut of one of her most famous characters, the Belgian sleuth Hercule Poirot. Christie would go on to become the world’s best-selling writer of mystery novels.

By the time Christie began writing, the mystery novel was a well-established genre with definite rules. Edgar Allan Poe pioneered the mystery genre in his short story “Murders in the Rue Morgue,” and writers like Sir Arthur Conan Doyle carried on the tradition Poe began. In traditional mysteries like Poe’s and Doyle’s, the story is told from the perspective of a detective-protagonist (or a friend of the detective, like Sherlock Holmes’s companion, Dr. Watson) as he or she examines clues and pursues a killer. At the end of the novel, the detective unmasks the murderer and sums up the case, explaining the crime and clearing up mysterious events. As the story unfolds, the reader gets access to exactly the same information as the detective, which makes the mystery novel a kind of game in which the reader has a chance to solve the case for him- or herself.

Fairly early in her career, in 1926, Christie came under fire for writing an “unfair” mystery novel. In The Murder of Roger Ackroyd, the killer turns out to be the narrator, and many readers and critics felt that this was too deceptive a plot twist. Christie was unapologetic, however, and today The Murder of Roger Ackroyd is considered a masterpiece of the detective genre.

And Then There Were None, written in 1939, breaks more rules of the mystery genre. No detective solves the case, the murderer escapes from the law’s grasp, and the plot construction makes guessing the killer’s identity nearly impossible. Despite this rule-breaking, or perhaps because of it, And Then There Were None ranks as one of Christie’s most popular and critically acclaimed novels. It was made into a stage play, and several film versions have been produced, the most celebrated of which is the 1945 version starring Barry Fitzgerald and Walter Huston.

In all, Christie produced eighty novels and short-story collections, most of them featuring either Poirot or her other famous sleuth, the elderly spinster Miss Marple. She also wrote four works of nonfiction and fourteen plays, including The Mousetrap, the longest-running play in history. Eventually, Christie married an archaeologist named Sir Max Mallowan, whose trips to the Middle East provided the setting for a number of her novels. In 1971, Queen Elizabeth II awarded Christie the title of Dame Commander of the British Empire. Christie died in Oxfordshire, England, on January 12, 1976.