Some of us were here when, thirty years ago, a plaid-clad little volume, The Official Preppy Handbook, became a surprise bestseller, even in seemingly unlikely places. Who knew that Lisa Birnbach so had her hand on the pulse of a sizable public? These many years later, the tenets of preppydom are revisited, and variously revised, by Ms. Birnbach and ace book designer Chip Kidd (who has said the publication of The Preppy Handbook when he was in the tenth grade changed his life), in the very entertaining new book, True Prep: It's a Whole New Old World (Knopf). All sorts of tips, practical and otherwise, are presented in high form, along with a lexicon of terms and traditions, all good for preparing one for knowing what's prep and what's not. Included are guest contributors such as Christopher Buckley (on being an 'aging' prepster) and Edmund White, with a travel narrative on gays and the preppy universe.