In ''A Fire in Their Hearts," Tony Michels explores a chapter in Jewish life that, he contends, scholars have long overlooked -- the rise of socialism among immigrants in turn-of-the-century New York. With a few key exceptions, he observes, historians have viewed Jewish socialism as a short-lived import from revolutionary circles in czarist Russia. Socialism, they say, equipped Jews with political skills but failed to have a lasting ideological effect; for the most part, Jewish socialists abandoned radicalism as they took their place in mainstream American politics and life. The dominant spirit in many histories, Michels argues, is celebratory --...