4.5 stars (a few formatting issues, but the content itself was exciting and entertaining).
My favourite thing about this book was the contrast between the two protagonists, Faith and Mackenzie. Faith was loud and proud and struggled with keeping her bipolar under control. Mackenzie was more reserved and worried too much. They often got on each other's nerves, but watching them meet in the middle and be best friends despite their differences was satisfying. Regarding the stalker/thriller aspect of the story, it was exciting and gave me chills. A little bit of why-would-you-do-that horror, but it was still satisfying and I was happy with the ending.