The Princess Bride by William Goldman
I'm about to horrify half of you, but the movie...
Than the book.
Unfortunately this is one of those rare exceptional cases where the director does a better job than the author. Some credit must go to William Goldman, however, for coming up with all the ideas in the first place. Any more goodwill, however, must be thrown out the window due to his decision to start of the book with 40 pages of Florinese history.
Don't let the title of this book deceive you. While it is a romance it is also an adventure of the most noble kind. There are pirates, giants, terrifying beasts, daring rescues, an evil prince, as well as a good sprinkling of humour - don't forget Princess Buttercup!
The movie captures all of this delightfully and is truly a classic to be enjoyed by all ages.
If you want to be a geek like us then by all means read the book! It gives wonderful back stories for the lesser characters like Fezzik and Inigo which really helps the reader to understand the complexity of the characters as well as see the worldbuilding that Goldman put into it.
So to sum up, the Princess Bride is one of the greatest stories...ever.
But the movie was better.