Who killed Alex?

International best-seller in 10 countries. Over 41 million reads. Wattys Award. Hannah is a sixteen-year-old student hooked on social media. One day, she receives a friend request on Facebook from a boy named Alex Crowell. After accepting it, Hannah discovers that Alex is missing and that he is given up for dead. However, an eerie event takes place: Hannah gets a message from the boy, who asks for help to find out who killed him. From that moment, she will start an investigation to track down the killer with Alex's ghost help. But facing the truth won't be easy for either of them