Well it's not very often I end up liking a movie more than the book, but this is one of those situations.
The Notebook was a great book, no doubt, but I wish it would have went more in-depth into Noah & Allie's past (the summer that they met). That is one reason I like the movie more: you actually get to see what happened that summer and how it came about that they fell so in love & remained that way for the rest of their lives. The book just BARELY skimmed over the details of their first summer & mostly focused on the later years, when they meet back up, & their old-age years.
It did make me cry, just like the movie, though ;]