If He Had Been With Me by Laura Nowlin: Throughout their whole childhood, Finn and Autumn were inseparable—they finished each other's sentences, they knew just what to say when the other person was hurting. But one incident in middle school puts them in separate social worlds come high school, and Autumn has been happily dating James for the last 2 years. But she's always wondered what if... The night she's about to get the answer, the unthinkable happens. Incredibly warm & heartbreaking.
Gillian Flynn on 6 Dark Books That Actually Scare *Her*