In a half-dozen previous novels, headed by "The High and the Mighty," Ernest Gann has at times effectively drawn upon his air and ground experience as a multimillion-mile pilot. The technical litany of a plane in flight. The diversely selected passengers bound by a taut situation to which they respond in diverse ways. The aloof and lonely skipper occupied with the terrible responsibility of craft and human lives. Add a bravura plot to hold dramatic material intact for passage in and out of the clouds or through the inscrutable back streets of Hong Kong and San Francisco, and the basic components are pretty well identified. Lacking the poesy of St. Exupéry, for instance, or the dazzling simple power of Capt. Joshua Slocum, Mr. Gann nevertheless writes colorfully of humans pitting themselves against the natural elements. [In "Twilight for the Gods" we] … have the drama as before except...