Gwendy's Final Task

When Gwendy Peterson was twelve, a mysterious stranger named Richard Farris gave her a mysterious box for safekeeping. It offered treats and vintage coins, but it was dangerous. Years later, the button box reentered Gwendy's life. A successful novelist and a rising political star, she was once again forced to deal with the temptation the box represented. The final book in the New York Times bestselling "Gwendy's Button Box"" trilogy from Stephen King and Richard Chizmar.