In the Moremi Reserve of the Okavango Delta, the Lewins and their guide Arabang search for elephants. Along the way, they spot termites, a leopard, giraffes, wild dogs and waterfowl, but no elephants -- until the very last day. Ted Lewin's full-color paintings are thrilling; they alternate with text-heavier pages lightened by Betsy Lewin's field sketches. It's great reading for Okavango-bound youngsters ages 6 to 10.  (BOT15, $15.95)