Darkside is a novel written by Dennis Etchison. It was first published in 1983.
Description[]
Don't Go near the darkside.
The anonymous warning appears in your mailbox. A stone, marked with an ancient symbol, is hurled at your door. And your daughter creeps out of the house in the dead of night.
The horror has begun.
You have stepped into a terrifying nightmare. You are walking the razor's edge of death. Bit it is too late to turn back.
You have entered the darkside and there is no escape.