I love how surprising this book is! From the title, you expect someone to be watching someone else. But soon you realize that there's more than one person watching other people. And then after some time, you don't know anymore who are the villains and who are the good people. And you start to question yourself about what will happen and how... and by whom. I also found very clever the fact that the narrative was intercalated with some of the police interview transcripts. So you learn from early on that a crime took place, but it takes a while to understand what exactly happened and to whom. Overall, this is a very surprising book, full of plot twists. I love when a book manages to be surprising all the way to the end!