Cross My Heart, Hope To Die (The Lying Game, #5)

Cross My Heart, Hope To Die (The Lying Game, #5) - Sara Shepard 2.5 stars.
Cross My Heart, Hope To Die is the fifth instalment of Sara Shepard's The Lying Game series. The books follow Emma Paxton, a girl who has been in and out of foster homes since age five. Then, one day, she receives a message from a girl who claims to be her twin sister. Willing to meet her, Emma ventures out to Tucson, only to find that her twin sister has been murdered. The murderer warns Emma that if she doesn't play along, and pretend to be her dead twin sister, Sutton, that she will be his/her next victim.
In each book, Emma has been pretending to be Sutton, in order to find out who killed her sister. Each book goes through a suspect, or two, only to find out that the person is innocent.
Cross My Heart, Hope To Die is no different.
I'm not particularly sure why, but I didn't like this book as much as I have liked the previous four in this series.
I didn't warm to the author's description of mental illness, and its effects on people's lives. I felt like she was demonising mental health patients, and I didn't appreciate the notion.
That aside, I felt like nothing much, in terms of plot development, occurred in this book. Emma went through another suspect; this time her mother. She had make-out sessions with her boyfriend, Ethan, and went shopping with Sutton's friends. It all felt a little repetitive.
Granted, the ending surprised me a little, and I am intrigued to find out what happens next in this story.
Oh, and I am definitely team Thayer (if there are even teams in this series). I like him a lot better than I like Ethan (I have my suspicions regarding this character - and they are not nice suspicions let me tell you).
I am also left wondering how many books are going to be in this series, and how long it will take to uncover the murderer.