Some biographies are weighty, definitive tomes that add substantially to the sum of human knowledge; others are brisker accounts that condense the existing record into a digestible narrative. This new biography of the African American novelist, critic and playwright James Baldwin falls squarely in the latter category, but is well worth a read. It examines the trajectory of Baldwin’s political thought on the interlocking questions of race, class and sexuality. At just under 200 pages, it is a smart and concise introduction to a writer whose trenchant insights into the nature of US politics and culture are as relevant today as they have ever been.

Bill V Mullen sees Baldwin as something of a reluctant radical. Though he associated with communists in his youth, and his analysis of the historical plight of African Americans drew from Marxist political economy (“we have been functioning … for 400 years as a source of cheap labour”), Baldwin had misgivings about the left. He noted with some bitterness that the discrimination routinely practised by many US trade unions made a mockery of the notion that black and white workers could find common cause in the labour movement. He had no truck with Soviet communism, advocating instead what Bobby Seale, the co-founder of the Black Panthers, called a “Yankee Doodle type socialism”.

Baldwin’s early engagements with racial politics were similarly equivocal. He was sceptical about the Negritude movement of the 1950s, which sought to mobilise solidarity among the global African diaspora. Baldwin saw himself as a “bastard of the west”, shaped by his experience of western modernity; tethering himself to an imagined African identity would belie that reality. Likewise some of the rhetoric of black militancy – notably the racial separatism advocated by groups such as the Nation of Islam – jarred with him because it merely reproduced, in reverse, the logic of white supremacy.

So what changed? Public events, Mullen writes, “pulled Baldwin out of his writer’s isolation and into history”. Ghana won its independence in 1957 and another 17 African countries followed suit in 1960. Baldwin believed this had a profound effect on how African Americans saw themselves and their place in the world. Reporting on a student march for racial equality in Tallahassee in 1960, he observed in the demonstrators a new and unprecedented assertiveness: “These students were born at the very moment at which Europe’s domination of Africa was ending.”

Baldwin saw the Vietnam war as an extension of US discrimination against its black minority: “A racist society can’t but fight a racist war.” Gradually, Mullen writes, “his former life as an African-American dissident was reborn in the guise of a cosmopolitan internationalist”. A decade riddled with white supremacist violence, culminating in the assassination of Martin Luther King in 1968, made him increasingly sympathetic towards the politics of direct action – including the policy of armed self-defence championed by the Panthers.

Mullen is a little harsh on Baldwin for not embracing LGBTQ activism more wholeheartedly. It is true that, when asked about the gay themes in his fiction, he tended to frame them in universal terms. He remarked that his second novel, Giovanni’s Room, which has cult status in queer literary circles, was “about what happens when you’re afraid to love anybody. Which is much more interesting than the question of homosexuality.” Far from being a cop-out, however, Baldwin’s willingness to draw on the gay experience to interrogate masculinity tout court was pioneering. In his 1985 essay, “Freaks and the American Ideal of Manhood”, he attacked the “American ideal of masculinity [that] has created cowboys and Indians, good guys and bad guys, punks and studs, tough guys and softies, butch and faggot, black and white … an ideal so paralytically infantile that it is virtually forbidden – as an unpatriotic act – that the American boy evolve into the complexity of manhood.” In spotlighting how machismo, through its “othering” of difference, informed the racist mindset, Baldwin laid the groundwork for what would come to be known as intersectional criticism.

His independence of thought is perhaps nowhere more evident than in his literary criticism, where he combined a small-c conservative intellectual rigour with an unerring sense of moral justice. He sniped at the excesses of high modernism, declaring: “I can see no virtue in art divorced from life or art which distorts and negates it.” At the same time, however, he took issue with the so-called “protest novel”, asking pointedly whether “its power as a corrective social force is sufficient to override its deficiencies as literature”, and insisting that dogmatic and sentimental social realism does a disservice to “the unpredictability and the occasional and amazing splendour of the human being”.

He lived out his last days in the idyllic town of St Paul-de-Vence in the south of France. Back home, the reactionary pushback against the gains made in the 1960s and 70s was well under way. “Reagan’s cruelty,” Mullen writes, “was merely a symptom of what Baldwin saw as the reconstitution of white supremacist ruling-class power in the United States.” That pushback is still in train today. While it is tempting to attribute the turmoil of the present moment to the singular machinations of the current president, the reality is more complex. To revisit Baldwin’s life and work is to be reminded that the US has been mired in violence and chauvinism for as long as it has existed.

• James Baldwin: Living in Fire by Bill V Mullen is published by Pluto ($27) To order a copy go to guardianbookshop.com or call 020-3176 3837. Free UK p&p over £10, online orders only. Phone orders min p&p of £1.99.