Gillian Flynn has a real gift for creating deeply unlikable characters and creating sympathy for them (or at least understanding). In all three of her novels, she creates point of view characters who are flawed in some way--and not the usual main character flaws, but some serious, messed-up, pathological flaws--and builds the story in such a way that the reader's understanding of the characters grows over the course of the story. That doesn't necessarily mean you like the characters at the end, but you certainly understand why they are the way they are. 
 In Dark Places, Flynn examines the Satanism panic of the 1980s and America's fascination with sensational crime. Libby survived the murder of her mother and two sisters, as well as her brother's conviction for the crime, but she (understandably) isn't doing well with her life. Twenty-some years after the murders, she's struggling financially and falls in with a group fascinated by the event who promise her money in exchange for contacting people she hasn't spoken to in years--including her brother. And maybe discovering what really happened that night will allow her some measure of healing.