Harris was "heavily involved" in the Occupy Wall Street movement. In 2012, he pleaded guilty and was convicted of disorderly conduct for his participation in an October 2011 Occupy protest on the Brooklyn Bridge. The court case became "a significant focus of attention for its involvement of posts to social networking sites and legal arguments over who controls that material," as the prosecution sought to undermine his defense using his own Tweets which he had deleted.
Harris's 2017 book, Kids These Days: The Making of Millennials, is a social critique of American millennials as human capital. In it, he explores the economic, social, and political conditions and institutions that nurtured American millennials and shaped them into a distinct group. Yohann Koshy wrote in the Financial Times that Harris argues that "society conspires to make life worse for young people," that "millennials are producing lots of value at work that is not reflected in job quality or wages," and that much of this applies to the United Kingdom too.
In 2020, he released Shit Is Fucked Up and Bullshit: History Since the End of History, a collection of essays written from 2010 to 2019 about the worsening of general life and politics in that decade, through topics such as gender, wages, millenials, Marx, and popular media.
During the COVID-19 pandemic, Harris spent time writing about his home town of Palo Alto, California. The resulting book, Palo Alto: A History of California, Capitalism, and the World, which was published in February 2023, details the history of that city and its role in the 21st-century U.S. economy, which is largely defined by the Internet and the electronic devices produced in Silicon Valley. One review of the book said that it is “nominally a history, but it is really a work of grand theory [...] Marxism” and describes a “capitalist horror show.”
↑Lennard, Natasha (Winter 2018). "The Kids Aren't Alright". Dissent Magazine. Archived from the original on September 28, 2019. Retrieved September 28, 2019.