Since I've done a large portion of my comprehensive reading on American labour history, I'll provide a number of sources both on labour historiography and broader histories of the American labour movement, the working class, and so on. Also, do you only want books or do you have access to scholarly articles as well?

Melvyn Dubofsky, Hard Work: The Making of Labour History (2000)

In this book, Dubofsky describes the transition from "Old Labour History," characterized by the "Commons School" approach that focused mainly on institutions - political and union - from a traditionalist economic standpoint, to "New Labour History" post 1960. The New Labour History, according to Dubofsky, is characterized by the tendency to expand examination into the lives of the working class, women, and minorities.

Leon Fink, Progressive Intellectuals & the Dilemmas of Democratic Commitment (1997)

In this book, Leon Fink explores the intellectual currents of late-19th and early 20th century American society. He pays particularly close attention to the relationship between the public and intellectual notions of democracy.

Fink examines the vacillation between the conservative notion that the broader public was incapable of intellectually coping with society and the leftist notion – expressed by thinkers such as John Dewey and Charles Merriam – that workers could be taught to press for progressive values. The growth of “Old labour history” through the Commons School reflects a response to these issues; it was imagined that “radical intellectuals” could bridge the gap between workers and “intellectuals.” From this impetus we see the growth of workers’ education initiatives; Ruskin College at Oxford is one example. These thinkers idealized the labour movement as an instrument of education, which did not turn out as they hoped. The AFL rejected these considerations, believing that “too much thinking” could be dangerous.

Fink, In Search of the Working Class (1994)

This is an excellent collection of essays that gives a historiographical overview of the developments of labour and working class history, as well as brief discussions of several relevant scholarly disputes, since the early 20th century.

H.G. Gutman, Work, Culture and Society (NY: Vintage, 1976)

Gutman's book is an early example of the New Labour History. He focuses on ethnic realities within the American working class, particularly examining the impact of immigration on class struggle, the dynamics of race within trade unionism, and the working-class challenges posed by workers in Paterson, New Jersey. Keep in mind, this is not the most up-to-date book, but an important addition to the field nonetheless.

David Montgomery. Workers' Control in America, Studies in the History of Work, Technology, and Labor Struggles. Cambridge, 1979.

This book is an articulation of workers’ understanding of control in the American workplace during the late 19th and early 20th centuries. David Montgomery illustrates the development of scientific management and Taylorism, and paints workers’ resistance against these controls as class struggle.

He begins by examining 19th century workers control actions, such as the imposition of stints and other methods. He continues on to describe Taylorist management strategies, developing factionalism within the AFL between socialists and hardline Democrats, and the consolidation of the Democrats within the House of Labour by 1916. Ultimately, he calls for us to question how the "labour movement" has become synonymous with the "union movement," and how other realities may have been possible.

David Montgomery. The Fall of the House of Labor. The Workplace, the State, and American Labor Activism, 1865-1925. Cambridge, 1987.

In his magnum opus, Montgomery traces the development of the AFL – the “House of Labour” – between 1900-1922. Importantly, he also focuses on “the common labour” – comprised largely by African Americans and immigrants – and describes a sort of “sojourner solidarity” that emerged within the lower strata of the working class by 1910. Montgomery also traces the development of specialized operative workers during the early 20th century, alongside the growth of scientific management principles. By the 1920s, many corporations had bought into corporate welfare policies and scientific management to underpin moderate unionism and combat radical influence. Concluding, Montgomery asks how we as a society might combine all avenues of working-class thought in the creation of a just system.

Alice Kessler-Harris, In Pursuit of Equity: Women, Men, and the Quest for Economic Citizenship in 20th Century America (Oxford: OUP, 2001)

This book examines how particular ideas of “fairness” became enshrined in American social institutions during the 20th century. Gender provides us with an analytical framework to examine how masculinity and femininity rationalized some policies and undercut others. The main theme of In Pursuit of Equity is how tradition/culture/race/gender helped shape conceptions of “fairness” that influenced 20th century social policy. This book also reflects the impact of women's and gender history on the study of labour history, I have some more examples of this stream of thought as well, if you are so inclined.

Additionally, although it isn't American, I would recommend E.P. Thompson's The Making of the English Working Class, as it is an extremely important text in modern labour history and has greatly influenced the American labour history discipline.

If you do have access to journals, I can provide a number of other works that relate to the above books, including some theoretical debates and developments within the field. If you have any specific interests regarding American labour history, such as particular unions, women, immigrants, African Americans, etc., just let me know and I'll see what I can dig up.

The original answerer has indeed given some of the best answers, but there are some other works that I have enjoyed, either as direct labour histories, or as important to the general American working-class and left movements. I am primarily a historian of Canadian labour and politics, but have a cursory knowledge.

Joseph A McCartin, Labor's Great War: the struggle for industrial democracy and the origins of modern American labor relations, 1912-1921 (Chapel Hill: University of North Carolina Press, 1997) Wartime labour struggles are often ignored by the public, especially those in WW1. This book is still likely the best on the matter

Melvyn Dubofsky, We shall be all: a history of the Industrial Workers of the World (Chicago: Quadrangle Books, 1969) As the first poster showed, Dubofsky is a legend in American labour history, but this book is important not only for its sheer length, but in its coverage of the IWW, a union many mainstream labour histories ignore or misunderstand

Elizabeth Cohen, Making a new deal : industrial workers in Chicago, 1919-1939 (Cambridge: Cambridge University Press, 2008) Not so much a pure labour history, but still a good look at labour and working class culture. A highly-acclaimed book

Matthew Piehl, Breaking Bread: The Catholic Worker and the Origin of Catholic Radicalism in America (Philadelphia: Temple University Press, 1982 The religious labour-left is also an understudied aspect of history in both Canada and the US, and this book gives an excellent example of Catholic socialists.

Denning, Michael. The Cultural Front: The Laboring of American Culture in the Twentieth Century. London: Verso, 1996. Not fully a labour history, this book is really key because it looks at the way traditional workers linked directly and philosophically with artists and writers. It is a book of great theoretical importance regarding the depression and the exciting political realities therein.

Kelley, Robin D.G. Hammer and Hoe: Alabama Communists During the Great Depression. Chapel Hill: University of North Carolina Press, 1990. Black workers are understudied, especially in their relationship with communism. This is my favourite book on the matter

Michael Honey, Southern Labor and Black Civil Rights: Organizing Memphis Workers (1993) This makes the often purposefully expunged links between civil rights leaders like MLK and the labour and socialist movements much more clear. Other works by Honey do an equally good job.