Lovable E.T. returns--in an effortful tale that has all the mawkish cuteness, mechanical burlesque, and catchpenny appeal of a hamburger commercial. E.T.'s home is the Green Planet, a world of plants: talking plants, jumping plants, shrieking plants. But, thanks to his adventures on Earth, Doctor of Botany E.T.--back home at last--finds himself disgraced and demoted. Disconsolate, he tries to contact distant Earth and friend Elliott by mental projection; but E.T.'s aim isn't very good. Furthermore, several years have passed on Earth, and Elliott has discovered girls--to the exclusion of everything else. So, aided by various friends, E.T. tries to steal a spaceship, gets caught, and ends up back among the plants. Next, he settles down to grow himself a spaceship, disguising it as a giant turnip. But finally one of E.T.'s mental projections finds its target. . . just in time to help Elliott outface a rival and earn his first kiss. Fitted out with saccharine prose and hand-puppet doings, this sequel to the film--and Kotzwinkle's big-selling novelization--has little of the movie's warmth or charm; and it's becoming harder and harder to remember that Kotzwinkle was once the hugely promising author of Dr. Rat and Fata Morgana. Still, with promotion that emphasizes that E.T.'s new adventures are ""based on a story by Steven Spielberg,"" you'd better count on substantial popular/YA demand.