HERE'S AN ILLUMINATING, spellbinding guide to the whole American horror phenomenon of the past 30 years (especially as it's surfaced in books, films and TV) by the gifted and industrious 34-year-old Maine author of a clutch of highly successful horror novels -- his recent The Dead Zone and Firestarter were both No. 1 on nationwide best-seller lists for extended periods.

To begin with, the alternately cleanshaven and black-bearded Down Easter scans his childhood memories to trace the growth of his own fears, feelings and insights about horror. He recounts listening to a radio adaptation of Ray Bradbury's chilling "Mars is Heaven!" on Dimension X and then sleeping in his bedroom doorway that night so he'd be in the light from the bathroom. And first seeing The Creature From the Black Lagoon at a drive-in movie from the car's back seat behind his mother and her date, his brother asleep beside him, knowing the thing he was watching had to be a man in a black rubber suit, but also gloomily certain the same figure would appear again lurking in his bedroom closet.

Or when his uncle Clay caught him dowsing and he felt the applewood wand dip strongly in response to dark underground forces or suggestions.

Or with other 10-year-olds on October 4, 1957, at a Friday matinee of Earth vs. the Flying Saucers where the evil root-creatures from outer space (but you sort of thought of them as the Russians too) destroy Washington, D.C., before being vanquished. "We were fertile ground for the seeds of terror, we war babies; we had been raised in a strange circus atmosphere of paranoia, patriotism, and national hubris." And how the strangely shaken manager stopped the film to announce that the Russians had successfully orbited a space vehicle they called Sputnik. Silence. Then a shrill, angry, tearful voice, "Oh, go show the movie, you liar!"

This was King's introduction to what he now calls society's and the individual's "phobic pressure points" -- national, political, economic, social, racial, environmental, technological, nuclear, as well as the universal fairy-tale fears we're all born with of the dark and death and evil parents or step-parents and the eat-you-up boogeyman. He defines horror writing (and filming) as "a moving, rhythmic search for the place where we live at our most primitive level" and the healthful purging of the fears there by the artistic creation and ultimate destruction or banishment of fiction's monsters. That's the ultimate justification of horror books and movies -- they feed the alligators of the unconscious, and so free us to love.

The fictional monster may have a super-natural or weird science character King analyzes Frankenstein (The Thing), Dracula (The Vampire) and Dr. Jekyll and Mr. Hyde, whom he treats as the Werewolf because of his animality and rages -- but it generally boils down to the merciless murdering maniac with the axe. This is particularly true in horror films, to which King devotes about half his space and all his photos.

The horror-movie jungle is a dark and dubious area where, because of the rushed production of cheapies and sensation-vying, there are six or eight barely mediocre or plain awful films for every one that's good -- The Exorcist or Jaws, say, or The Seventh Seal or Orpheus or The Phantom of the Opera or King's own Carrie, done into a fine movie by Brian De Palma. (But not King's The Shining, expensively botched by Stanley Kubrick or, just conceivably, turned into slow-motion black comedy.) On the junk side, films with titles like Green Slime, My Bloody Valentine, The Night Evelyn Came Out of the Grave (they sold red popcorn at that one), or The Horror of Party Beach.

But King shows how you can cultivate a medical-student sense of humor against the excesses of these films and even sometimes find an overlooked jewel such as Tourist Trap, Eyes Without a Face, The Texas Chainsaw Massacre, The Night of the Living Dead, Phase IV, or Duel.

It's not that their bloody murders condemn these sub-films, you see. The first three Greek tragedies I can think of are pretty extreme in that direction: A wife and her lover stab her returned soldier husband while he's taking a bath and more killings logically ensue; a man murders his father and lays his mother, she hangs herself and he tears out his own eyes; a king who doubts the devine powers of healing drunkenness is torn to pieces by crazy women (Euripides' Bacchae).

It's that there are no powerful feelings, guilts and empathies, to go with the bloody murders in the cinematic trash and make us feel a general pity for all -- no catharsis -- which is just King's basic point about horror all over again: The fear has got to get at you, even gross you out, before there's healing.

When it comes to treating horror novels, King understandably tends to favor and discuss at length those which have been made into films: The Shrinking Man by Richard Matheson, The Haunting of Hill House by Jack Finney, which he uses to illuminate the phobic pressure points of political and social paranoia; and Rosemary's Baby by Ira Levin. Also Peter Straub's beautifully styled Ghost Story, currently being made into a film. And the very recent The House Next Door by Anne Rivers Siddons. But King doesn't neglect his fellow horror writers: Ray Bradbury (Something Wicked This Way Comes), Ramsey Campbell (The Doll Who Ate His Mother), Robert Bloch (psycho -- there's more about Bloch in King's introduction to his own collection, Night Shift), and the hyperkinetic Harlan Ellison, half street-guy and half god, whom King quotes at length.

It think of these four, incidentally, along with King himself, as the five enfants terribles of the horror story. Why King. Well, his boyish delight in shocking and talking dirty, for one thing. His clowning -- he invites the reader to waltz with him in the dark, heh-heh. (danse Macabre, get it? As kids they pronounced it "McBare" -- there's a William Castle horror flick titled Macabre. The chuckle's from the Old Witch in Tales from the Crypt, a classic horror comic of the 1950s.) King's zesty love of grossing you out, if he can't terrify or horrify you first. Although he knows its uses, he doesn't favor restraint in horror writing. Take Salem's Lot. With a gambler's passion King believes in showing the reader the worst, the monster in full figure, nothing held back -- shoot the works! -- and if the reader's not scared then, well, back to the drawing board, men.

At one point, King gets far enough away from film influences to say that the two best horror novels of the past 100 years are Shirley Jackson's The Haunting of Hill House and Henry James' The Turn of the Screw, and right after them H. P. Lovecraft's At the Mountains of Madness and Arthur Machen's The Great God Pan. A case could be made for them.

There's much fascinating writing and film gossip in the book. For instance, King spent six weeks on a novel, "The House on Value Street," about the SLA and the Patty Hearst kidnapping, but never got it off the ground -- he wrote The Stand instead, in which a plague kills off almost everyone in the world.

But whatever Stephen King's writing, one thing always comes through: his love of the weird tale, the horror story, the ghost story -- to the point of a great and generous enthusiasm for the works of his fellow writers. I can't help liking that.