What would have happened if Elvis Presley's real-life twin, Jesse Garon, hadn't died at birth? That's the premise of Duff's third novel (Indian Giver, 1983, etc.), a mildly engaging southern yarn telling the life story of the King's unknown double. Duff portrays the twins' mother as a mystic who's heavily influenced by the moon. She has a revelation on the night she gets pregnant with the two boys, and later on decides to send Jesse off to live with nearby relatives. ``Elvis is light, and you're the heavy one,'' she tells him. ``Elvis rises up and you live in the world.'' In other words, Elvis gets to be a prima donna while Jesse must suffer like an ordinary schmo. What's worse, he has to do Elvis's dirty work. By the fifth grade, Jesse (who's also impersonating his brother at school by then) is beating up bullies who've picked on sensitive little Elvis. Years later, he gets his brother through the high school talent show; and it's Jesse who records at Sun Studios, but Elvis who gets the credit. When the King is too bloated and nervous to perform on the Ed Sullivan show, Jesse comes to the rescue and shakes his moneymaker like Elvis never could. Jesse runs off to far-flung places in order to try to make a separate life for himself, but he's repeatedly drawn back to save Elvis. He even prolongs his brother's marriage by making love to Priscilla when Elvis himself has lost interest. After his twin dies, Jesse becomes the best Elvis impersonator on the planet. Duff has a deft comic touch, but he's mining a familiar vein and shedding little new light on the icon. Reading this one is like watching Viva Las Vegas on a sunny Sunday afternoon: slightly amusing, but mowing the lawn might be just as fun.