Darkness on the Edge of Town by Brian Keene

One morning the residents of Walden, Virginia, woke up to find the rest of the world gone. Just . . . gone. Surrounding their town was a wall of inky darkness, plummeting Walden into permanent night. Nothing can get in - not light, not people, not even electricity, radio, TV, internet, food, or water. And nothing can get out. No one who dared to penetrate the mysterious barrier has ever been seen again. Only their screams were heard. But for some, the darkness is not the worst of their fears. Driven mad by thirst, hunger, and perpetual night, the residents of Walden are ready to explode. The last few sane prisoners of this small town must prepare a final stand against their neighbors, themselves, and something even worse . . . something out there . . . in the darkness.