An interesting satire
This was definitely a unique kind of story with hilarious satiric wit (if you like that kind of humor). Goldman peppers his narrative with mix-ups of Biblical stories and theological non sequitors, notes on why he "abridged this part of the original Morgenstern novel", and complaints about how his editor wouldn't let him change this-and-such. Reading through these last got tedious after the first two page-long notes, though his italicized remarks on what his reactions were when "his father read the book to him" when he was little were amusing.
Though for the most part the movie version of "The Princess Bride" follows the book, there are significant differences - instead of having his Pit of Despair, Prince Humperdinck has a Zoo of Death; Princess Buttercup's feelings toward Westley actually develop through the story; and the back stories of Inigo, the revenge-obsessed Spaniard, and Fezzik, the slow-witted giant, are told in detail.
The book raises more moral problems than does the movie version, and this was specifically what brought the rating down, as well as the occasional swearing and its irreverence toward God. It is not a book meant to be original: it is a book making fun of a completely cliche storyline...and it does a good job at that.