Watch: 'The Rainmaker's Milo Callaghan, John Slattery Reveal How the Iconic Novel Came to LifeCourt is now in session. Nearly three decades after John Grisham's best-selling legal novel The Rainmaker first graced screens in Frances Ford Coppola's star-studded 1997 film, John Slattery and Milo Callaghan are breathing new life into the story with their USA Network courtroom drama. And that means taking a whole lot of creative liberties to stretch the story it across the 10-episode first season.