Quite possibly the Rainbow Rowelliest book that Rainbow Rowell has ever Rainbow Rowelled. Which, if you've read her other adult fiction, should make plenty of sense. If you haven't, then idk how to explain it. 

Am in a v emo place right now, and cried a few times while reading this. Read half of it in one sitting before bed, then the other half in a second sitting when I got up. 

If you don't like stories where the premise hangs on mis/poor communication, you're probably going to have a bad time with this. But it worked for me.