Average.. Cannot classify as a psychological thriller.. As soon as I found out about Jack's intentions, which happens quite early in the book, I just wanted to go directly to the end to know if Grace was able to escape and save her sister or not. They failed escape attempts were repetitive and boring and sometimes I felt that Grace wasn't using her brain well enough to use the opportunities well when she was taken outside the house or when she had people over.. eg. Millie's party when everyone was there. Overall a decent read.