Finding Cinderella Book by Colleen Hoover

A chance encounter in the dark leads eighteen-year-old Daniel and the girl who stumbles across him to profess their love for each other. But this love has conditions: they agree it will only last one hour and it will only be make-believe.
When their hour is up and the girl rushes off like Cinderella, Daniel tries to convince himself that what happened between them only seemed perfect because they were pretending it was perfect. Moments like that with girls like her don’t happen outside of fairytales.