The End of Everything — Megan Abbott

Thirteen-year-old Lizzie Hood and her next-door neighbor, Evie Verver, are inseparable, best friends who swap clothes, bathing suits, and field-hockey sticks and between whom -- presumably -- there are no secrets. Then one afternoon, Evie disappears, and as a rabid, giddy panic spreads through the balmy suburban community, everyone turns to Lizzie for answers. Was Evie unhappy, troubled, or upset? Had she mentioned being followed? Would she have gotten into the car of a stranger?

Compelled by curiosity, Lizzie takes up her own furtive pursuit of the truth. Haunted by dreams of her lost friend and titillated by her own new power as the center of the disappearance, Lizzie uncovers secret after secret and begins to wonder if she knew anything at all about her best friend.