Pittinger, Mark. Class Unknown: Undercover Investigations of American Work and Poverty from the Progressive Era to the Present. New York: New York University Press, 2012. 276 pp. US$25.00 (paperback). See original article here: Pittinger, Mark. Class Unknown: Undercover Investigations of American Work and Poverty from the Progressive Era to the Present. New York: New York University Press, 2012. 276 pp. US$25.00 (paperback).