In 1968 Mr. Rosengarten was a Harvard graduate student who went to Alabama with a friend who was researching a defunct organization called the Alabama Sharecroppers Union. Someone suggested they speak to Mr. Cobb, then 84.

Image Credit... Courtesy of Theodore Rosengarten

Mr. Rosengarten relates what happened: “We asked him right off why he joined the union. He didn’t respond directly; rather, he ‘interpreted’ the question and began, ‘I was haulin’ a load of hay out of Apafalya one day ...’ and continued uninterrupted for eight hours. He recounted dealings with landlords, bankers, fertilizer agents, mule traders, gin operators, sheriffs and judges — stories of the social relations of the cotton system. By evening, the fire had risen and died and risen again, and our question was answered.”

No fool, Mr. Rosengarten returned many times, over several years, to speak with Mr. Cobb. He’d found a powerful American voice, one that cracked open a world never so fully explored in print. The result is “All God’s Dangers,” which deserves a place in the front rank of American autobiographies.

There are many reasons, in 2014, to attend to Ned Cobb’s story. It is dense and tangled social history, a narrative that essentially takes us from slavery to Selma from the point of view of an unprosperous but eloquent and unbroken black man. In some ways, the book is a reverse photographic image of “Let Us Now Praise Famous Men,” the 1941 classic from James Agee and Walker Evans. Agee and Evans scrutinized the lives of white tenant farmers; in “All God’s Dangers,” we witness a black tenant family through three generations. The book is Faulknerian in its weave. Mr. Cobb’s working years, Mr. Rosengarten notes, “span approximately the same years as the Snopes family odyssey in William Faulkner’s trilogy.”

The book has its share of drama. We read about Cobb’s joining the radical union, about getting into a shootout with police while protecting a friend’s property from a fraudulent foreclosure, about his 12-year prison stint. But, in general, it moves gently; it’s more a stream than a river.

You will learn more about wheat, guano, farm implements, bugs, cattle killing and mule handling than you would think possible. Mr. Cobb loved and took good care of his working mules. About one, he declares: “She was just as pretty as a peeled onion.”

“All God’s Dangers” also happens to be a dense catalog of the ways that whites tricked and mistreated blacks in the first half of the 20th century. “Years ago I heard that Abraham Lincoln freed the colored people,” Mr. Cobb says early on, “but it didn’t amount to a hill of beans.” About his white neighbors, he declares, “Any way they could deprive a Negro was a celebration to ‘em.”