First up we have Every You, Every Me by David Levithan
Really super obvious, but the song I had stuck in my head the entire time I read this book was this:
I'm still debating over whether the song suits the book but in some ways my whole associating this song with Cruel Intentions doesn't help either. I think it kind of does because I assume the song is talking about various sides of a person which both the book and the movie have too right? That's what I think anyway. Let me know what you think!!