How to write, according to the bestselling novelist of all time

EVERYONE HAS a book inside them, or so the saying goes. In this day and age, those who want help coaxing the story out can receive instruction online from some of the world’s most popular authors. Lee Child and Harlan Coben, who have sold hundreds of millions of books between them, teach thriller writing; Jojo Moyes offers tips on romance yarns. And now Agatha Christie, the world’s bestselling writer of fiction, with more than 2bn copies sold, is instructing viewers in the art of the whodunnit—even though she died in 1976.