This book is a slow burn and then explodes. The focus is obviously on the sister in a coma and how her past and current life are slowly revealed. There is one expected red herring towards the beginning but then the true twists happen and they land each time. 

The last 1/3 of the book, there is a reveal every few pages and they all work and push the plot and character reveals. The MC is relatable for most of the book. A woman in a job that isn't that fulfilling, with a boss that is rude, a marriage that is strained but she wants it to work and the insecurities that result from both. 

The supporting cast of her sister and her husband are a good foil of one another that adds to the overall tension. Even the very brief appearance of the parents adds more to the story. Overall this thriller was well crafted and it shows. 

Content warning: There is some use of sexual assault that seems wholly unnecessary and doesn't add anything to the plot. I think this would have been a 5 star read for me if not for that addition.