I love Rob Reiner's film adaptation of this book. I love it so much, that I just kept putting off reading the book, because I didn't want to ruin the film. What I feared would happen was that either the book would be too good, and the film would appear crummy by comparison, or the book would be crummy, and I'd be left wondering exactly what the hell it was I liked about the film in the first place.
Fortunately, neither of those things happened. The movie is a faithful enough adaptation, so that most of the time I was reading it I was actually just pretty much playing the movie in my head, but not so faithful that there was absolutely nothing new, either. I still don't think the book is quite as good as the movie (I don't care what anyone says, reading the line, "I died that day," is just not nearly as heartbreaking as hearing Robin Wright scream it), but there are some things the book does very well that the film does not.
For example, the book's false abridgement is just a very clever idea. It was first published in 1973, the era of Vietnam, and pretty much uniformly depressing Hollywood movies. In order to have this sort of escapist romantic pulp accepted by both the public and the critics, Goldman needed to put some sort of ironic, depressing undertones in the book, making it palatable to a populus who had given up on happy endings. But if he had put the ironic, depressing stuff into the story proper, it would have made the book less fun, thus taking away its central appeal. So the ingenious strategy he came up with was to have the ironic, depressing stuff be a fictionalised autobiography about him and his attempts to abridge the story of The Princess Bride (written by the fictional S. Morgenstern) from an often tedious social satire to a fast paced adventure story. This way, the readers were able to be suitably depressed by the story of the failing marriage and the strained father-son relationship, feel suitably cool and hip for appreciating the ironic "I'm abridging a book that doesn't really exist" parts, and also, secretly, deep in their heart of hearts, be swept along by the romantic adventure stuff. The self-awareness gives people the right to enjoy the totally un-self-aware bits.
Also, the abridgement meant that Goldman didn't have to write any of the boring crap parts that he couldn't be bothered with. And it allowed him licence to write some pretty damn funny jokes.