The Murder of Roger Ackroyd by Agatha Christie (1926)

The concept of a narrator of a detective story has been prevalent for a long time. The most famous probably being the character of Dr. Watson from Sherlock Holmes who was the perfect foil to Sherlock Holmes. There are some expectations from the narrator of a good detective novel - the narrator can bring their own quirks to the story, but they are expected to layout the story in the way that it actually happened. You don't really expect the narrator to have a significant presence in the story; this was the concept that was used before the advent of this novel.
The Murder of Roger Ackroyd turned this whole concept upside down. Here was a narrator who was going along normally like most narrators, and then at the end, there is a huge element of surprise. Hercule Poirot points out that the murder was committed by the character of the narrator, and the narrator admits this as the last element of the story before committing surprise.



This twist in the novel was very controversial. After all, the concept of a good detective novel was that you provide the same clues to your reader as available to the detective, and if you hide a major element in the story (such as the narrator having done the killing), then it would almost seem like a break to that concept. Fortunately for this novel and Agatha Christie, except for some critics and reviewers, everybody else accepted this twist easily enough. In fact, many consider this to be among her best works.
The story is about the double murder in the small town of King's Abbott in England. The murder of Mrs. Ferrars happens first, and then the murder of Roger Ackroyd clears the lingering doubt about Mrs. Ferrars death was a murder. There are a variety of suspects with their different motives, with suspicion falling strongly on Ralph, the stepson of Roger Ackroyd backed by many pieces of evidence. And then Poirot steps in, having newly arrived there. What does Poirot do to absolve Ralph of the crime ? As usual, Agatha Christie has spun a great tale.