Jag tror att det här är Endless Night av Richard Laymon.
Jody is pretty tough for a sixteen-year-old girl. That's the only reason she's still alive - for now. She was sleeping over at her friend Evelyn's house when a group of killers broke in and tried to slaughter everyone. She saw Evelyn spitted on a spear, but Jody managed to escape, along with Evelyn's little brother, Andy. — Simon was one of the killers that gruesome night. His friends have left it up to him to find the only living witnesses to their massacre. Or else they'll butcher his family next. But Simon has his own reasons for wanting to get his hands on Jody...