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I've finally taken the plunge and read my first Stephen King book -- which is my disclaimer way of saying that, for all I know, what I'm about to write may be no-duh to longtime King readers. It's what struck me after reading Needful Things, though, so I'll say it anyway. (And before anyone rides me on a rail for being King-ignorant [Kingorant?], I've got Misery on my shelf to read soon.)
This book is (so I'm told) not King's most horrific writing, nor his most frightening, though I would call it frightful. What struck me so deeply was not the fact that the Devil comes to town as a well-groomed shopkeeper looking to con some people out of their souls, but that the town goes to hell on the highway of their own paving. Human greed and pride rule the day here, and while the people of Castle Rock may push their vices to the extreme, they act in ultimately human ways -- ways in which, under the right circumstances, you and I might well behave.
King could have actually made the story more frightful by backing off on the shopkeeper's control over human characters. Throughout the novel and up to right near the end, his powers of mental persuasion and delusion remain evident and only grow more powerful. I had the very real sense that the townspeople were being played -- not merely manipulated, but moved around the board like stiff, non-living chess pieces by an all-powerful hand. Persuasion is not the name if the game so much as domination. Yes, human desire for physical possessions (and the attendant jealousy and greed that fester like aggravated cold sores) courses through all the characters -- but we don't need the subordinating hand of a demonic salesman to induce magnificent and irrational destructive behavior. You don't even have to wait for Black Friday to observe how covetous normal people can be. Even your run-of-the-mill advertisements recognize this covetousness and employ incredible amounts of psychological influence on the human mind when it comes to triggering "need" rather than mere "want"; basically, what the impish shopkeeper in this book does to his customers, people themselves do to others anyway.
Yes, a satanic proprietor can exacerbate the worst of our qualities. The traits are already there, though. The frightful part of Needful Things is not that the Devil has ridden into town; it's what we're capable of doing with a little nudging. And all I have to do is look around my own reality to see that perhaps, in some ways, King overestimates just how much evil influence we might actually need to jump off the deep end.