One of my personal favorites, great for endless re-reads. When he wrote this, the author was unaware of the (now well-known) short story by F. Scott Fitzgerald, The Curious Case of Benjamin Button. But this story also focuses on a character who ages backwards, it just does so better than Button, both the movie and the story.
I'm a very cynical person, I don't cry at books and movies, but I find this one absolutely heartbreaking in the best, most beautiful way possible.