Responses
That's one way to put it. I just see the book as one parallel universe while this story line is in another and the book slipped into their world on accident.
It's from the timeline where Biff Tannen is president and Marty's mom has fake tits...
ROFL!!! OMG! xD yes, yes, that's perfect... Now I want to watch that trilogy again ;-; shame they never got around to making the fourth one.
I was looking through the comments and people are discussing about the purpose of the book. I think we should consider the fact that the book is in a third person perspective. "They lived happily ever after." in a third person perspective. Sangjin could still be holding true feelings for Songwoo in the "happily ever after" ending. -it's the perspective of someone not involved in the character's life, someone observing from the sidelines seeing Songwoo as just a friend(side character)
I don't think the book is pushing Songwoo and Sangjin together (as I read in other comments about how they should've been able to confess to each other already). In one of the flashbacks, we see the red book. I think this is another red book, like there are multiple fates. Think of it like a game, there are checkpoints where your decision sways the future, which means Songwoo giving her advice at that point was a "checkpoint" that could lead their fate into another path.