FACES TO WATCH WILLIAM TESTER

William Tester calls his first novel, Darling, a coming-of-age story, which is true as far as it goes: Tester's yarn hinges on a carnal courtship of the family cow and other things that would make Holden Caulfield blush. ''It's all true....And it's all not true,'' the author says of his novel, a sad, strange + story powered by evocative detail. Born of ''God-conjuring mystical hillbillies,'' the 31-year-old Tester grew up among the scrub and swamps of Florida. He says he had virtually no primary education and got into Columbia University's undergraduate writing program in 1978 by submitting an essay about being chased by a ball peen hammer. And at Columbia, he met novelist Gordon Lish, who ''pulled the novel out of me.'' Its creation took five years, during which Tester survived in Greenwich Village with the help of a National Endowment for the Arts grant and by modeling and selling his blood. ''I hope the NEA doesn't chase me down over the book,'' he says earnestly. ''God, it is bestiality.'' Tester is nervous about what to expect from more than the NEA when Knopf publishes Darling, arriving in bookstores now. ''It's a tough bucket to carry. I just hope it's read by people who would read this kind of book.'' And just what kind of people would they be? ''Not farm boys,'' he says.