I really really enjoyed that book. Sienna is a smart girl and she can fight. I love girls who fight. She's strong and can take care of herself. At first I felt sorry for the life she had (she was locked up in her house by her mother with plenty of rules like, always stay fully clothed, never talk about the outside world, etc, etc. She was basically a prisonner) but then I realised that those things moulded her into the person she is now. This book is also full of action and I liked the fact that Robert did not put much emphasis on her feelings about Zack. The girl's a fighter, survival comes first, and he stuck to that. Why 4 stars though, is because of the lack of information about why Wolfe and his employers needed her, and the fact that Wolfe kept showing up unexpectedly everywhere annoyed and bored me at times. And also because we know practically nothing about her mother and where she's disappeared to, what she was up to and stuff like that. But apart from that, this book is really nice and is kinda fast and throws you directly in the plot from the beginning itself. READ IT.