I'll tell you why so serious

The story-telling is good with flashbacks.The film is both funny and heartbreaking. You smile in a scene and get a soulcrushing revelation in the next.

The movie's neither hopeful in contrived ways, nor hopeless in different contrived ways. Somehow it manages to be wonderful

It's the kind of movie you'll want to see a second time with someone who hasn't seen it yet, to remember what it was like to watch it for the first time.