I hated every single character in this book (maybe Cathy could be an exception, But I didn't like her either) and I hated everything they did throughout the book. So why the four stars? Well, because I think that was the author's intention. She wanted you to dislike them all, to distrust everyone in order to keep the mystery. The book itself could have been more fast-paced, but other than that, it did the job wonderfully. I got more and more interested the more I advanced and although the ending was a bit predictable, in no way was it less engaging.
Also, I can't help pointing out that we have three women as main characters and all three of them are unemployed and living their lives only for the men they are connected with. None of them had any interest other than men. That could have been intentional, too, so I didn't consider it for my rating.
So, in short, I had a great time reading this book, I was interested until the end and I would recommend it. Four stars!