She wrote over 100 books, many of which were published under various pen names, including:
* Gladys Mitchell: Her most well-known pen name, used for her series featuring Mrs. Bradley, a formidable amateur detective. The Mrs. Bradley mysteries are considered classics of the Golden Age of detective fiction.
* Lorna Reade: Used for several romance novels.
* Mary Mitchell: Used for some of her historical fiction works.
Some of her most popular books include:
* The Saltmarsh Murders (Mrs. Bradley series)
* The Case of the Frightened Lady (Mrs. Bradley series)
* Death at the Vicarage (Mrs. Bradley series)
* The Dancing Foot (Mrs. Bradley series)
* The Case of the Missing Lady (Mrs. Bradley series)
* The Man Who Died Twice (Mrs. Bradley series)
* The Black Curtain (Mrs. Bradley series)
* The Mystery of the Missing Man (Mrs. Bradley series)
* The Murder at the Vicarage (Mrs. Bradley series)
* The Queen's Fool (Historical fiction)
* The Story of Love (Romance)
Note: While she used multiple pen names, her work under the name Gladys Mitchell is considered her most significant and is what she is best known for.