Who is Jacques Pepin and where does he stand? That's a baffling question for anyone who tries to reconcile his imposing, if not pretentious, two-volume Art of Cooking with this undiscriminating mishmash of dishes whose only common characteristic is their ease of preparation. With the dubiously applicable justification that ""In France it is quite common for even great home cooks to buy certain prepared foods,"" Pepin offers here some perfectly good but not uncommon simple dishes (grilled pork chops with rosemary; broiled red mapper with lemon vinagrette; broiled eggplant slices with a soy-based sauce); some fast but fancy creations (bread rolls stuffed with scallops, ginger, and cilantro and baked; brie tortilla croque-monsieur), some Betty Crocker-ish practicalities (leftover turkey salad), and a surprising lot of quickie concoctions, from pardonable to tacky, that use frozen pie-crusts, bread dough, puff pastry, mixed vegetables, and even frozen hashed-brown potatoes. Nor does Pepin miraculously redeem these conveniences with transforming ""techniques,"" as his subtitle promises; he merely lends his name to an undistinguished performance. Today, far more thoughtful and attractive quick-cooking books abound.