Mr. X by Peter Straub

Every year on his birthday, Ned Dunstan is cursed with visions of horror committed by a savage figure he calls "Mr. X." This year, Ned's visions will become flesh and blood. A dreadful premonition brings Ned home to find his mother on her deathbed. She reveals the never-before-disclosed name of his father and warns him of grave danger. Driven by a desperate sense of need, Ned explores his dark past and the astonishing legacy of his kin. Accused of violent crimes he has not committed and pursued by a shadowy twin, Ned enters a hidden world of ominous mysteries, where he must confront his deepest nightmares. . . .