It's an incredible movie. I'm not sure how much you should know before going in, but I'll say this: Don't be fooled by the fact that it's animated - by the same studio as "My Neighbor Totoro". (The two movies played as a double feature because not showing something lighthearted after Grave of the Fireflies would have been criminal negligence.) And the other comments are right - It's not something you're likely to be able to watch again anytime soon.