They're baaack! Now that the holiday gorging season is over, diet books are once again de rigueur. All three Rodale South Beach titles by Dr. Arthur Agatston are back on the PW charts; a fourth Rodale title, David Zinczenko's The Abs Diet, lands just below the top 15. The South Beach Diet, back on at #4, has eight million copies in print after 30 printings; The South Beach Diet Cookbook goes back at #13, with 1,950,000 copies after four trips to press; and The South Beach Diet Good Fats/Good Carbs Guide hits the trade paper list at #7 with 3,680,000 copies in print after eight printings. Abs has 327,000 copies in print.