MrBeast's new challenge: Convincing fans to buy his first book

MrBeast, whose real name is Jimmy Donaldson, is now an author. HarperCollins/Kristina Bumphrey/Getty Images MrBeast wants to turn fans of his videos into readers of his first book. The YouTuber is running a $1 million contest for people who buy the novel, which debuted Tuesday. The book is a team-up with James Patterson and was at No. 18 on Amazon's new releases list Monday. MrBeast is the king of stunts. His next big challenge? Convincing his more than 500 million YouTube subscribers to log…