This article relates to the 2004 novel. For the legal practice, see Rule of four.The Rule of Four is a novel written by the American authors Ian Caldwell and Dustin Thomason, and published in 2004. Caldwell, a Princeton University graduate, and Thomason, a Harvard College graduate, are childhood friends who wrote the book after their graduations.The Rule of Four reached the top of the New York Times Bestseller list, where it remained for more than six months.