SON OF THE GAMBLIN' MAN (333 pp.)Marl SandozClarkson N. Potter ($5).
A DISTANT TRUMPET (629 pp.)Paul MorganFarrar, Straus & Cudahy ($5.75).
Were all U.S. fiction written by American regionalists. man's mind might often seem to have no mountains; all might appear one vast, pre-Freudian plane. There are deft, complex exceptions, such as Kentucky's unjustly forgotten Elizabeth Madox (The Time of Man) Roberts, Nevada-bred Walter Van Tilburg (The Ox-Bow Incident) Clark. But generally the regional writer is a landscape artist, pure and psychologically all too simple. What is best in his books is...