Why is Agatha Christie regarded as the queen of detective fiction?

Hercule Poirot often tapped his forehead and said “These little gray cells. It is up to them – as you say over here”. Hercule Poirot was the Belgian detective with the egg shaped head, created by Agatha Christie. Poirot appears in Christie’s first detective novel, ‘The Mysterious Affair at Styles’. Miss Marple was Christie’s other famous fictional detective.

Christie’s father died, when she was a child. Her mother encouraged her to write at a very early age. In 56 years, Christie wrote 66 detective novels. She entertained more people for more hours at a time than any other writer of her generation.