Atonement

This book was only so-so. The movie was slightly better. The movie was a faithful adaptation until the very end. The book's effective Afterword has the author telling us that "maybe" she changed some details in order to give the lovers a happy ending.

In the movie, the author flat-out informs us that both her sister and Robbie did, in fact, die during the war, and were never able to enjoy their love.

While much sadder, this makes for a more fulfilling ending - no ambiguity.