Author of such classics of 20th-century popular American literature as "Tobacco Road" (1932) and "God's Little Acre" (1933), Erskine Caldwell was something of a celebrity nearly all his life. But he was also a serious writer, one whose merits are as considerable as they remain underexplored. In the 1930s, he startled the literary world with his frank portrayals of the poor whites of the South. Beginning in the early 1940s, critics grew suspicious that he had exhausted his originality and his talent. In the late 1960s, some scholars began an effort, which continues intermittently today, to...