Jonathan Franzen’s sixth novel, “Crossroads,” is set in 1971, and the title is firmly on the nose: the Hildebrand family is at a crossroads itself, just as the America of that moment seemed poised to come apart. In the course of his career, Franzen has evolved away from an early postmodernist sensibility that highlighted “bravura” writing, and “with this book I threw away all the po-mo hijinks and the grand plot elements,” he tells David Remnick. “It’s really only in the course of writing ‘Crossroads’ that I have said to myself, What I am is a novelist of character and psychology. . . . It’s not about formal experimentation and it’s certainly not about changing the world through my social commentary.” Franzen also discusses the complex ethics behind writing a character of another race, and takes issue with the belief of some in the academy (and much of the political right) that leftist sensibilities are stifling free expression; he declined to sign the “Harper’s Letter” last year. Despite political polarization, Franzen says, “It’s a much better time to be an American writer than I would have guessed twenty-five years ago.”