Truth be told, I wish I could have experienced the story without knowing it already. For as I've said, it's a marvelously faithful adaptation. One of the better book-to-screen transfers out there. Yet it would have been nice not to know the identity of the "man in black" or what the great plan for storming the castle would be. Even though I adore all the actors and their performances, I could not help but use their faces and voices while reading the book so I couldn't really form my own perceptions. Fortunately it's all wrapped up in a little more info and background than the movie is able to give, so it did have a freshness as well.
There are a couple of changes in the film which I think work much better than the original story. Both come at the end. Don't worry, the book and film have very similar endings. For all intents and purposes it plays out to the same effect. But it seems that having a chance to revisit it, some new ideas came to Goldman. For one, when Westly is lying on the bed after being mostly dead he does not have the powerful moment of standing up as he does in the film. Also in the film, Westly suggests to Inigo that he'd make a good Dread Pirate Roberts - but not in the book. I'm glad these changes were made, as each moment is much more effective and logical.
Thank you, William Goldman, for your work. It's truly remarkable and we're so glad it had not been inconceivable.