Other Agatha Christie Novels

Periodically, Agatha Christie deserted her established sleuths such as Poirot and Marple and wrote novels with entirely new characters or else characters who appeared in other books in supporting roles. Sometimes, the stories were entirely standalone books 

Below is a list of those standalone novels

The Sittaford Mystery (1931)

Why didn't they ask Evans? (1934)

And Then There Were None (1939)

Death comes as the end (1944)

Crooked House (1949)

They came to Baghdad (1951)

Destination Unknown (1954)

Ordeal by Innocence (1958)

The Pale Horse (1961)

Endless Night (1967)

13 at Dinner (1969)

Passenger to Farnkfurt (1970)