A notice to those who feel that Stephen King has lost his magic touch: Desperation is the genuine goods. The ensemble cast of ordinary Americans thrown together by chance, including a disgruntled alcoholic writer and a child who is wise beyond his years, may be a bit too familiar. But the nearly deserted Nevada mining town with an enormous haunted mine pit and an abandoned movie theatre where the survivors hang out makes for a striking battleground, and the grisly action rarely flags. Best of all, though, are the characters of Tak, the ancient body-hopping evil who emerges from the mine, and of "God"--whom the New York Times describes as "the edgiest creation in Desperation. Remote, isolated