From seat No. 9, Hercule Poirot is almost ideally placed to observe his fellow air travelers on this short flight from Paris to London. Over to his right sits a pretty young woman, clearly infatuated with the man opposite. Ahead, in seat No. 13, is the Countess of Horbury, horribly addicted to cocaine and not doing too good a job of concealing it. Across the gangway in seat No. 8, a writer of detective fiction is being troubled by an aggressive wasp. Yes, Poirot is almost ideally placed to take it all in—except that the passenger in the seat directly behind him has slumped over in the course of the flight…dead. Murdered. By someone in Poirot’s immediate proximity. And Poirot himself must number among the suspects.

• Times Literary Supplement: ‘It will be a very acute reader who does not receive a complete surprise at the end.’

13. The ABC Murders (1936)

Captain Arthur Hastings returns to narrate this account of a personal challenge made to ‘Mr Clever Poirot’ by a killer who identifies himself as ‘ABC’ and who leaves the ABC Rail Guide next to his victims—apparently intending to work through the English countryside (he has struck in Andover, Bexhill-on-Sea, and Churston) and exercise Poirot along the way. Serialized in London’s Daily Express, The ABC Murders became a cultural phenomenon as readers were invited to try to keep up with the famous Belgian detective. It is a challenge that remains fresh and thrilling to this day—and makes The ABC Murders one of the absolute must-reads of the Christie canon.

• Julian Symons: ‘A masterwork of carefully concealed artifice… most stunningly original.’
• Sunday Times: ‘There is no more cunning player of the murder game than Agatha Christie.’

14. Murder in Mesopotamia (1936)

Nurse Amy Leatheran had never felt the lure of the ‘mysterious East,’ but she nonetheless accepts an assignment at Hassanieh, an ancient site deep in the Iraqi desert, to care for the wife of a celebrated archaeologist. Mrs Leidner is suffering bizarre visions and nervous terror. ‘I’m afraid of being killed!’ she admits to her nurse. Her terror, unfortunately, is anything but unfounded, and Nurse Leatheran is soon enough without a patient. The world’s greatest detective happens to be in the vicinity, however: having concluded an assignment in Syria, and curious about the dig at Hassanieh, Hercule Poirot arrives in time to lead a murder investigation that will tax even his remarkable powers—and in a part of the world that has seen more than its share of misadventure and foul play.

• The New York Times: ‘Smooth, highly original, and completely absorbing.’

15. Cards on the Table (1936)