It is one of Christie's best known and most controversial novels, its innovative twist ending having a significant impact on the genre. The short biography of Christie which is included in the present UK printings of all of her books states that this novel is her masterpiece. Howard Haycraft, in his seminal 1941 work, Murder for Pleasure, included the novel in his "cornerstones" list of the most influential crime novels ever written. The character of Caroline Sheppard was later acknowledged by Christie as a possible precursor to her famous detective Miss Marple.