Mary Roberts Rinehart was a prolific writer that is often referred to as the American Agatha Christie. Rinehart's mystery novels are still treasured by millions of readers today and she is the source of the famous phrase "The butler did it." Rinehart's most famous books include The Circular Staircase, The Bat, The Case of Jennie Brice, and The Door. Bab: A Sub-Deb is a humorous novel that is set during World War I. Bab, the title character, is a spoiled yet neglected second daughter from a rich family. The book is presented in the form of letters and diary entries.