Stephen King Unleashed; He's back on the best-seller list. But now he wants more. Much more

Stephen King, highly successful author of horror novels, has had his books regularly listed on The New York Times best-seller lists; lately, however, his novels have spent fewer weeks on the lists; King, at age 51, is aggressively dealing with highpoint of long career; his new novel, Bag of Bones, centers on popular author who develops severe case of writer's block following his wife's death; King is hoping romantic elements in Bag of Bones will result in book's selling better than anything he has done in years; year ago King left his publisher, Viking, which became part of Penguin Putnam Group; since then, King developed a unique profit-sharing partnership with Simon & Schuster; some critics believe King's book sales were too flat to justify the almost $18 million advance he initially demanded for Bag of Bones; chart on how King ranks against authors Michael Crichton, John Grisham and Tom Clancy in terms of estimated income, best-selling hardcover books and movie adaptations from books (L)