I heard about this book on the A Little Bit Culty podcast when they interviewed the author. The story is about a group of teens who lived on a commune that ended up being a cult when their defacto leader got more grandiose and paranoid. The book goes back and forth between current day, where the adults haven't seen each other or stayed in much contact since a traumatic event and the breakup of the cult, and their time there growing up. In the present, they all start to receive letters that imply someone knows about their involvement in whatever event made the cult break up, and blackmails them into getting back together to go back and figure out what is going on. I enjoyed the book and likely would even if I hadn't listened to the podcast, but knowing that the author had brushes with multiple culty situations throughout her life made it seem even better somehow.