In the 1980s Clapp, a documentary filmmaker by trade, set out in pursuit of the lost city of Ubar, a fabled center of the ancient Arabian frankincense trade. With the aid of NASA satellite photographs and a troop of scientists, he succeeded where the likes of T.E. Lawrence and Berthram Thomas had long since failed, finding the ruins of Ubar in Oman's "Empty Quarter". This is his fascinating day-by-day account of the search.  (ARB49, $19.95)