AN AMERICAN VISITOR (247 pp.)Joyce GaryHarper ($3.95).
Most of today's countless novels about Africa offer a paraphrase of headlines, a splash of truculent social justice, and a dubbed-in romance. To see how shallow they can be, one must compare them with the late Joyce Gary's African books, which may not seem attuned to the latest news, but which even today make the news more intelligible. Gary fought in the Nigeria Regiment in World War I, later served as a magistrate dealing with the everyday crises of tribal life. Out of this experience came Mister Johnson (published in 1939), by all odds...