The Cabin (used book) - Natasha Preston
There may only be one killer, but no one is innocent.
When Mackenzie treks to a secluded cabin in the woods with six friends, she expects a fun weekend of partying, drinking, and hookups. But when they wake to find two of their own dead and covered in blood, it's clear there's a killer among them.
As the police try to unravel the case, Mackenzie launches her own investigation. Before long secrets start to emerge, revealing a sinister web of sins among the original seven friends. The killer is still free. Every one of them is a suspect. And Mackenzie starts to realize that no one is innocent…