The Murder of Roger Ackroyd (1926) is a detective novel by Agatha Christie. The book, set in the fictional village of King's Abbott in England, features the detective Hercule Poirot.
Warning: Wikipedia contains spoilers
The story is told in the first person by Dr James Sheppard. It begins with the death of Mrs. Ferrars, a wealthy widow who is rumored to have murdered her husband. Her death is initially believed to be suicide until Roger Ackroyd, a widower who had been expected to marry Mrs Ferrars, dies. The suspects include Ackroyd's niece, Flora, Major Blunt, a big-game hunter, Geoffrey Raymond, Ackroyd's secretary, Ralph Paton, an adopted son with gambling debts, and Parker, a snooping butler.
Warning (yet again): Wikipedia contains spoilers
The book is most notable for its surprise ending in which it is revealed that the narrator is the murderer: