Them — William W. Johnstone

Jake Silver was a teenage misfit, a misunderstood genius who'd been cruelly tormented by his own sadistic father and others in his little Louisiana hometown. Jake was the perfect disciple for THEM.

They'd come from another world;disembodied beings who understood Jake's need for revenge... They would offer Jake the power to finally take it... All they wanted in return was his help in bringing others of their kind to Jake's world.

It began so slowly, so innocently, even Jake didn't see the danger...until it was too late to realize that he had helped unleash a devastating power in the universe--and opened a gateway for a horrific struggle between mere human beings and ...THEM