why did The Murder of Roger Ackroyd receive so much criticism

Considered by many to be Christie’s masterpiece, the novel is nonetheless controversial for it’s stunning ending. Christie admitted she got the idea for the ending from her brother-in-law, James Watts, who mused on a detective novel in which the criminal turns out to be the “Dr. Watson” character, referring to Watson’s position in Sir Arthur Conan Doyle’s Sherlock Holmes series as the companion and chronicler of the brilliant detective.