Girls Who Burn by M.K. Pagano

When eighteen-year-old Addie’s sister is found dead at the bottom of a ravine, it’s officially ruled an accident, but Addie doesn’t buy it. The problem is, Addie has no evidence because when her sister died, she was a little distracted with Seth Montgomery, the boy next door Addie’s always loved to hate. She believes the murderer is Thatcher Montgomery, Seth’s cousin. He always had a thing for her sister, and Addie caught them arguing shortly before her death. But, one year later, Thatcher is found dead at the bottom of the same ravine and Addie is forced to admit she was wrong… Read more.