The movie The Princess Bride was released originally in 1987, and did okay but not great while in theaters. It really came into its own on home video and today is considered a classic movie, having last year been added to the National Film Registry for being "culturally, historically, or aesthetically significant."
The movie is based on William Goldman's novel The Princess Bride which was published in 1973. I've owned the book for a few years, but only got around to reading it about six months ago. I'm going to assume that most people are very familiar with the film and not relate the plot, but rather discuss the differences between the book and movie.
My copy of the book is the 25th anniversary edition and it includes a sample chapter which is supposedly from the sequel to The Princess Bride: Buttercup's Baby, which is about Waverly, the infant daughter of Westley and Buttercup. Goldman is apparently working on this sequel, which he has said will be released in 2023, the 50th anniversary of the original novel.