Agatha Christie was a writer.
Agatha Christie . She is best known for her 66 detective novels and 14 short story collections , particularly those revolving around her fictional detectives Hercule Poirot and Miss Marple . She also wrote the world 's longest-running play , a murder mystery , The Mousetrap , and six romances under the name Mary Westmacott . Guinness World Records lists Christie as the best-selling novelist of all time . Christie 's stage play The Mousetrap holds the world record for longest initial run .