The Princess Bride is one of the most charming and entertaining fantasy movies ever made. Simply brilliant.
It was written by a man who became one of my most favorite screenwriters over the years: William Goldman.
(He also wrote the screenplays for several other movies I love - Butch Cassidy and the Sundance Kid, The Hot Rock, The Stepford Wives, The Great Waldo Pepper, Marathon Man, All the President's Men, Misery.)
For some reason screenwriters rarely get the credit they deserve, even though they were the ones who created all those characters and dialogues the fans love so much. I recommend Goldman's book Which lie did I tell? which contains an interesting chapter on Princess Bride.
OT: Nice to see these guys together again (but where's Mandy Patinkin?). Robin Wright looks better today than in 1987.