Robert R. McCammon - Usher's Passing (Ballantine 1985, Original Holt, Rinehart and Winston 1984, 407 p.)
The House of Usher has towered over a century with its apocalyptic warning against the powers of madness and evil. Yet the House of Usher is nor mere tale. And neither did it really ever fall.
Today the House of Usher is a multibillion-dollar corporate empire standing poised on the brink of its most devastating onslaught against an unsuspecting world … crafting fantastic superweapons that can level the planet … summoning demons of destruction from the darkest reaches of the earth.
Unless one young heir to the House of Usher can, at long last, break the unyielding spell of terror. Before it breaks him.
The cover blurb is a bit vague. Basically it is about an American dynasty named Usher which inspired Poe to his story. (Who gets a small cameo in the prologue) All descendants are suffering more or less from the sickness described in Poe's tale. Now the patriarch lies dying in Usherland, the family seat somewhere in North Carolina, while the feuding family comes together. One son is a struggling horror writer who has cut all ties to the family money, the other is a bully, the daughter is a model. The writer, who is the main protagonist, discovers something supernatural about his family, while a monster is prowling the backwoods and the inbred hillbillys living there.