Don't Look Back - Jennifer L. Armentrout

Samantha is a stranger in her own life. Until the night she disappeared with her best friend, Cassie, everyone said Sam had it all-popularity, wealth, and a dream boyfriend. Sam has resurfaced, but she has no recollection of who she was or what happened to her that night. As she tries to piece together her life from before, she realizes it's one she no longer wants any part of. The old Sam took "mean girl" to a whole new level, and it's clear she and Cassie were more like best enemies. Sam is pretty sure that losing her memories is like winning the lottery. She's getting a second chance at being a better daughter, sister, and friend, and she's falling hard for Carson Ortiz, a boy who has always looked out for her-even if the old Sam treated him like trash. But Cassie is still missing, and the facts about what happened to her that night aren't just buried deep inside of Sam's memory-someone else knows, someone who wants to make sure Sam stays quiet. All Sam wants is the truth, and if she can unlock her clouded memories of that fateful night, she can finally move on. But what if remembering is the only thing keeping Sam alive?