In the quiet village of King’s Abbot a widow’s suicide has stirred suspicion—and dreadful gossip. There are rumours that she murdered her first husband, that she was being blackmailed, and that her secret lover was Roger Ackroyd. Then, on the verge of discovering the blackmailer’s identity, Ackroyd himself is murdered. Hercule Poirot, who has settled in King’s Abbot for some peace and quiet and a little gardening, finds himself at the centre of the case—and up against a diabolically clever and devious killer.

Of note: The Murder of Roger Ackroyd broke all the rules of detective fiction and made Agatha Christie a household name. Widely regarded as her masterpiece (though perhaps it may be called her ‘Poirot masterpiece’ since other titles in her canon—notably And Then There Were None—are similarly acclaimed), The Murder of Roger Ackroyd was the source of some controversy when it was published. The Times Literary Supplement’s praise of the first Poirot, The Mysterious Affair at Styles, ‘almost too ingenious,’ was applied by scores of readers to Ackroyd, who were nonetheless enraptured by the novel, and have remained so over the decades.

Fair warning: There are two things you must do if you know nothing of the book: discuss it with no one, and read it with all speed.

• H.R.F. Keating: ‘One of the landmarks of detective literature’ (in his Crime & Mystery: The 100 Best Books).
• Julian Symons: ‘The most brilliant of deceptions’ (in his Bloody Murder: From the Detective Story to the Crime Novel).
• Irish Independent: ‘A classic—the book has worthily earned its fame.’

5. The Big Four (1927)

Hercule Poirot is preparing for a voyage to South America. Looming in the doorway of his bedroom is an uninvited guest, coated from head to foot in dust and mud. The man’s gaunt face registers Poirot for a moment, and then he collapses. The stranger recovers long enough to identify Poirot by name and madly and repeatedly scribble the figure ‘4’ on a piece of paper. Poirot cancels his trip. An investigation is in order. Fortunately, Poirot has the faithful Captain Hastings at his side as he plunges into a conspiracy of international scope—one that would consolidate power in the deadly cabal known as ‘The Big Four.’

6. The Mystery of the Blue Train (1928)

Le Train Bleu is an elegant, leisurely means of travel, and one certainly free of intrigue. Hercule Poirot is aboard, bound for the Riviera. And so is Ruth Kettering, the American heiress. Bailing out of a doomed marriage, she is en route to reconcile with her former lover. But her private affairs are made quite public when she is found murdered in her luxury compartment—bludgeoned almost beyond recognition. Fans of the later novel Murder on the Orient Express will not want to miss this journey by rail—and Poirot’s eerie reenactment of the crime…

7. Black Coffee (1930; 1998)