Ok, this book was un-putdownable! I felt like the mystery and the tension just kept ramping up until the very unpredictable end! 

I was on the edge of my seat - the mysterious emails that Natalie gets (Natalie who still has survivors guilt from the accident that caused her mother's death many years ago), the creepy/weird vibes I got from Simon, the accident in the Caribbean that gives Natalie PTSD, her interesting relationship with her stepsister Isabel... All lent to a very compelling story.