Unbelievable (Pretty Little Liars, Book 4) by Sara Shepard

Unbelievable is the fourth book in the bestselling Pretty Little Liars series by Sara Shepard, where the central mystery of the girls’ tormentor, “A,” is seemingly resolved for the first time. The novel focuses on the aftermath of Hanna’s car accident and the girls’ final push to uncover the truth about who killed Alison DiLaurentis.