In a sense, Thomas Mallon's fictional portrait of Tim Laughlin in "Fellow Travelers" supports the real-life themes of a new book by Joshua Zeitz called "White Ethnic New York: Jews, Catholics, and the Shaping of Postwar Politics." Exploring the Irish as well as other ethnic enclaves, Zeitz argues that Irish Americans and other Catholics remained deeply unmelted even after Word War II, when many people believed they'd simply faded into the vast American middle class and became like everyone else. "Between the 1940s and the late 1960s, New York's three largest white ethnic groups, Jews, Italian Catholics, and Irish Catholics, numbered as many as 4.3 million people, roughly two thirds of New York's white population and more than half of its total population," Zeitz recently wrote in American Heritage, describing his book. "In New York, for instance, in any given year upwards of two thirds of all Catholic children from kindergarten through eighth grade were enrolled in parish schools. At home and in parish schools, generations of Catholic New Yorkers internalized a respect for public and religious authority and a general skepticism of radical dissent, attitudes that were at once the product of their religious subculture and a reflection of their predominantly homogeneous working-class environment." ($24.95 / 296 pages / North Carolina)