Bill Belichick was assured by his book publicist just days before his now-infamous sitdown with "CBS Sunday Morning" that his interview for the show would closely stick to topics related to his new book ... TMZ Sports has learned.
Sources familiar with the situation tell us ... back on April 9, Simon & Schuster's senior director of publicity, David Kass, wrote to Belichick, "I can assure you that the conversation [will be] about the book."
"This is a book segment," Kass added, "that looks at your life in football and what people can learn from you to achieve success in their own lives.