Agatha Christie was a writer.
Agatha Christie . Her novels have sold roughly 2 billion copies , and her estate claims that her works come third in the rankings of the world 's most-widely published books , behind only Shakespeare 's works and the Bible . 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 Mousetrap is a murder mystery play by Agatha Christie .