The King Is Dead : TENDER <i> By Mark Childress (Harmony Books: $19.95; 566 pp.) </i>

On a cold winter night in a northern Mississippi shack, a baby is born to teen-age parents. The baby is dead. After placing the body on the dresser and covering it with a pillowcase, the doctor takes the bad news to the stunned father pacing the front porch.

Back at the bedside of the mother, the doctor is surprised when she goes into labor again. The second baby, the lucky twin, breathes and howls with life after a ritual slap.

Later, at the request of his wife, Agnes, Ray Kirby takes the dead infant from its shoebox-sized coffin, resting in the shack’s front room. He carries the corpse to Agnes. She nestles the tiny blue body in her arms with its living brother. She urges her husband to join the three of them in the bed. He does.

And so the hard-luck Kirby family has its first and only full night together. The haunting episode hardly seems the beginning of an American success story, a rise to fame and fortune powered by an $8 guitar, a pile of pomaded hair, swivel hips, loud clothes and a priceless knack for turning teen-age girls into screaming, clothes-ripping, record-buying, hormonal mobs.

But it is.

The surviving twin is John Leroy Kirby, the shy, narcissistic, mother-dominated hero of “Tender,” Mark Childress’ third novel. Destined to be bigger than sliced bread and richer than almost anybody but Howard Hughes, Leroy Kirby--the name by which he becomes known to the world--is the prototypical rock star, the guy who defines the field by inventing it.

Kirby, not so incidentally, bears a striking resemblance to Elvis Presley, the popular culture demigod who died in 1977 but has gained a kind of eternal life through the obsessive devotion of his fans, a faith so persistent that many claim to have seen him alive, well and passing through gas stations, doughnut shops and bowling alleys.

Possibly, the publisher is betting that the parallels between Leroy and Elvis will help sell the 50,000-copy first printing. For people who can’t get enough of the Elvis legend, the novel’s 566 pages could be tantamount to bathing in the King’s favorite soft drink.

On the other hand, there are enough points of divergence from the historical Elvis for the author and publisher to maintain plausible deniability. Notably, Leroy’s manager is most definitely not Col. Tom Parker, who is mentioned in the book as being busy elsewhere.

Details aside, “Tender” stands on its own as an evocation of an American phenomenon and the time and place that nurtured an ascent to glory. Childress gets everything right, from the poverty of Tupelo, Miss., to the glittering haven that mid-century Memphis seemed to the Kirbys, who skip to Tennessee because Ray, already with a stretch in the pen to his credit, may be busted for pig-stealing.

“Tender,” which follows Leroy until he is drafted into the army, also is an uncanny portrait of adolescence and the awakening of world-class ambition and talent in a boy who got a guitar because his family couldn’t afford a bicycle. In the end, of course, Leroy feeds his hunger for wheels, buying so many pink Cadillacs, motorcycles and assorted other vehicles that his mother says he can always open a used-car lot if he flops in the music business.

In fact, the novel itself moves with the velocity of a chromed 1950s Detroit beast. Once it is revved up and rolling, “Tender” carries Leroy down destiny’s highway with the easy power of a gas-guzzling V-8. And once you’re snuggled down in the leatherette upholstery, you don’t want to stop, just tune in the radio and ride it to the end, the way Leroy does--until the army barber takes all his famous hair.

But be careful to slow down and enjoy the good moments. Like the one about the Kirbys’ triumphant return to Tupelo. Apprehended on the way by state policemen, the Kirbys all share an anxious moment until they learn the cops are their escort into town. Father Ray is certain he’s finally going to be hauled in for stealing that pig. Meanwhile, Leroy is sure his lack of a driver’s license is going to lead to national humiliation.

Beneath these funny interludes, however, there are portents of trouble ahead. Leroy begins taking pills and smoking marijuana. His mother becomes a recluse hooked on brandy, chocolate-covered cherries and sedatives. By the time the army gets him, the paint is peeling off Leroy’s life and the motor has started to miss. More ominously, Leroy has begun to hear again the voice of his dead baby brother, a voice that deserted him during the heady years of his success.

By the end of the book, the voice of his mother, killed by her son’s long absences from home and the tolls of publicity, has joined the twin. This spooky duo makes Leroy’s isolation complete. You know he’s ready for the long, downhill trip, where the wheels come off.