In this wintry, supremely elegant collection, Byatt (Possession) peels back the surface of everyday life -- and what she reveals may disturb your sleep. In ''The Pink Ribbon,'' a genteel old man buys his Alzheimer's-stricken wife a stuffed Teletubby, then stabs and mangles it late at night. In ''The Thing in the Forest,'' two small girls see -- or think they see -- a giant, malodorous worm while playing in the woods; they never discuss the creature again, but the encounter haunts them throughout their lives. And in the devastasting ''Raw Material,'' a writing teacher finds his ideal student in a prim elderly woman who describes old-fashioned washday in violent, sensual, and stunning prose. What little he eventually learns about her life is, like the rest of this chilling volume, beautifully described and decidedly ''not nice.''