The Project by Courtney Summers
Lo Denham's sister, Bea, joined The Unity Project after their parents died. The Unity Project appears to be the perfect group due to their extensive charitable work and community outreach. But Lo knows the truth: it's a cult, and she's determined to prove it. When she's given the opportunity to investigate the group on assignment from her magazine, Lo jumps at the chance. But as she dives deeper into the group, it changes everything she thought she knew about her sister, herself, cults, and the world around her.
Review from Publishers Weekly:
Nineteen-year-old Lo Denham’s name isn’t short for lonely, but it could be: after her parents died in a car accident that scarred Lo and left her near death, her adored older sister Bea joined the Unity Project, an insular Upstate New York religious group that’s constantly fighting accusations of culthood. Lo longs to be a writer, but though she’s landed a job at a Vice-like magazine, also upstate, she’s stuck as its editor’s assistant. When she witnesses a suicide that turns out to have links to the Unity Project, she embarks on an investigation of the secretive, seemingly well-meaning group and her sister’s whereabouts. By turns driven, vulnerable, and impulsive, Lo gets closer and closer to the Project’s charismatic, damaged leader, risking everything to find the truth. Alternating Lo and Bea’s viewpoints and moving around in time, Summers (Sadie) makes effective use of each character’s limited knowledge, creating a twisty plot that’s full of hooks.