David Westheimer's novels of World War II continue to appear with the regularity of military reunions, and Rider on the Wind (Walker: $13.95) is another comfortable story, albeit camouflaged by a standard olive-drab theme. The airman-hero of this tale is the kid navigator, not an aircraft commander with nerves of titanium. Their bomber is a B-24 as aeronautical relief from all that literary glamour poured upon B-17s. And, instead of Warmbeer-on-Wold, Lincolnshire, 1944, these Yanks are occupying the enemy and the local ladies from Ramat Jonas, Palestine, 1942. All of which give us "Twelve O'Clock High" meets "Exodus," and if you haven't had enough of the camaraderie of combat air crews, boys becoming men in flight suits and the sack, and love in the desperation of wartime negating national differences and ideals (but not quite in time), then here are three friendly hours.