Agatha Christie is a towering figure in the history of crime literature for two reasons. First, she consolidated the form of the pure mystery novel, achieving in five or six of her books puzzle stories that set a standard unlikely ever to be decisively bettered. Second, she sold more books than any other writer except Shakespeare. Totaling her sales was a task that defeated her agent and publishers. Her works have been translated into more than a hundred languages. She was, in short, the most successful mystery writer the world has known.

To some extent Christie's extraordinary success can be attributed to timing. Christie began writing at the start of the Golden Age of the detective story, when mysteries were attaining worldwide popularity. As she continued to turn out books, her name became in the public mind almost a shorthand expression for the genre. Her increasing popularity had...