Agatha Christie was a writer.
Agatha Christie . She also wrote the world 's longest-running play , a murder mystery , The Mousetrap , and six romances under the name Mary Westmacott . And Then There Were None is a mystery novel by English writer Agatha Christie , widely considered her masterpiece and described by her as the most difficult of her books to write . The Murder of Roger Ackroyd is a work of detective fiction by Agatha Christie , first published in June 1926 in the United Kingdom by William Collins , Sons and in the United States by Dodd , Mead and Company on 19 June 1926 . Witness for the Prosecution is a play adapted by Agatha Christie from her short story .