IT may be helpful to call attention from time to time to those books which are exciting enthusiasm among the sophisticates, and in which there ought to be sustained interest. This month I have three that I would trust to any fastidious fancier of novels. First, a short book about which it is hard to speak too highly — The Trader’s Wife, by Jean Kenyon Mackenzie (Coward-McCann, $2.00), a story of such distinction and economy as has not appeared in a long time. I think of it as a first, cousin to Ethan Frome. Secondly, Look Homeward, Angel, by Thomas Wolf (Scribner’s, $2.50), a story of the South and, so the saying goes, of Asheville, North Carolina, the first three quarters of whose six hundred pages are sure promise of a fresh American talent. Finally, Innocent Voyage, by Richard Hughes (Harper’s, $2.50), that bright, touching, sardonic book of last spring, now republished.