This book is so lovely and so clear, and, judging from the number of times Rosenzweig's name comes up in the Acknowledgement sections of other books, he's a wonderfully nice guy, too.
Therefore, his study of working-class people in Worcester might not be generalizable to the nation, but it has a wealth of detail on Swedish wireworkers, the fight for a park in Ward 5, Irish drinking habits, the Protestant-Catholic divide, and what people really did in working-class movie theaters at the turn of the century (they brought their kids and talked - a lot! Alamo Drafthouse would not approve.)
And as a result of these specific details, Rosenzweig is able to draw some interesting conclusions about why Worcester was considered a 'scab hole' with a chronic open shop problem: the immigrant communities there were so insular and so different from one another that they were unable to unite across ethnic, cultural, or religious lines. Further, some issues, particularly the fight over working-class saloons, not only divided the working class (Irish Catholics vs Swedish evangelicals) but allowed for some cross-class alliances (particularly among non-drinking Protestants), thus splintering the working class further. And this splintering worked to the benefit of the industrialists but to the detriment of the workers, who couldn't lobby for shorter days or higher pay as effectively as could workers in other towns.
However, like the workers in David Gartman's Auto Opium, the working classes in Worcester had a weakness for the new mass culture and mass entertainment, and they were eager patrons of amusement parks and movie houses when these came to town. Unlike Gartman, however, Rosenzweig sees this working class obsession with consumption not as an opiate but as an incredible boon to his subjects. To patronize amusement parks and movie houses, people had to come out of their ethnic enclaves and mingle with people of other religions, ethnicities, cultures, and sometimes even other classes. This new mass mingling in new leisure spaces, combined with rising incomes and the development of a new ethnic middle class, led to less antagonism within the working class itself, which in turn provided a foundation for more radical political activism in the 1930s and 1940s.
Basically, modernization and the rise of mass consumer culture at the turn of the century was both the problem (creation of a culture of individual accumulation) and the solution (break down intra-class divisions so the working class can fight its oppressors later on down the line.) Or at least Rosenzweig hopes so.