Most Europeans, if asked what they know about Indian society, would mention ‘the caste system’; some might add ‘untouchability’. But few could say much more about what these terms mean, and the tone in which they refer to the subject tends to be abstract and detached. Contrast this to the way in which people speak of apartheid, anti-Semitism or chattel slavery. In the moral narrative of world history, Indian society has, thanks to Western ignorance of caste and the fact of British colonialism, got off rather lightly.

When it comes to untouchability, there is plenty of ignorance in India too – of the wilful kind. For readers who know little about it, Sujatha Gidla’s family memoir will irrevocably change how they see India. But even a reader who has read everything on the subject will be changed by this book, forced to confront reality more directly, moved and discomfited in equal measures.

Untouchables, now usually called Dalits in India, are not so much at the bottom of the caste hierarchy as outside it: forced to live beyond the margins of the village and denied access to communal resources, whether material or cultural. Some work on the fields of the landowning castes (in the Indian village, land is power), while others are condemned to those occupations that caste Hindus consider beneath them, such as ‘manual scavenging’ (the collection of human faeces) and the handling of dead animals. Their treatment by caste Hindus extends to levels of violence that recall the days of Jim Crow.

There are over two hundred million Dalits: they make up at least a sixth of India’s population. It is on this scale that the oppression and violence Gidla describes occurs, but her family’s story is highly particular.

Gidla’s ancestors were part of a ‘nomadic clan’ that was driven out of the forest where they roamed by the British. They settled near a lake and took up agriculture, until they encountered the caste Hindus, who gradually seized their land and imposed upon them the status of untouchables. This is, she writes, the story of all ‘tribal peoples in India who try to settle down and cultivate land’. But Gidla’s family did not remain landless labourers. They were converted to Christianity by missionaries and given access to what the untouchables had been denied through the ages: education. One of her grandfathers, Prasanna Rao, overcame great hardship to become a charismatic and successful teacher.

This is partly how Gidla herself came to study and work at two of India’s most prestigious engineering colleges, and later to migrate to the United States. Ants Among Elephants is not the story of her own life, however, but that of the two generations that preceded her. If it has a protagonist, it is K G Satyamurthy, her maternal uncle, known as Satyam.

Satyam, who died in 2012, was an important figure in the Maoist Naxalite guerilla struggle that, since the 1960s, has sought to mobilise landless peasants and Adivasis (indigenous tribes) against landlords and their ultimate guarantor, the Indian state. He was a cofounder of the People’s War Group, the main Naxalite force in the state of Andhra Pradesh. To the young Sujatha Gidla, Satyam was a ‘cinema hero’; to his many followers, he was both prophet and exemplar.

His story, from his intellectual formation as a teenager, drawn equally to scientific socialism and Telugu poetry, to his career as a Communist Party activist turned armed revolutionary, forms the main narrative thread and links to broader social and political themes. But the less public stories of Gidla’s mother, Manjula, and Prasanna Rao are just as compelling.

The story Gidla recounts is so urgent and affecting that it is easy to overlook the extraordinary literary skill with which she tells it. Her prose is limpid and perfectly paced; the sociological exposition she provides enriches the narrative, and vice versa. Like Katherine Boo in Behind the Beautiful Forevers, she turns years of interviews into a story told from inside its characters’ minds.

There are really two books here: the story of a family and the story of a country. Narratively, they fit seamlessly together, on the same page and even in the same paragraph. Nonetheless the method that makes the book so powerful as a memoir makes it a little less reliable as social or political history. Events are described as the characters saw them, but the author, decades later, does not interrogate or fact check their claims.

Near the end Gidla, writing in her own voice, says that while she revered her uncle, she did not agree with many of his ‘programmes and tactics’. What is missing is either some authorial scepticism towards his version of history or an acknowledgement that it is his version and ought to be treated as such. Instead we have statements that purport to be factual but are anything but (‘beef … in India is eaten only by untouchables and Muslims’; ‘the whole of south India was contained in the Madras Presidency’). Her version of Communist Party history has been contested by some of Satyam’s contemporaries. None of this, though, detracts from the moral weight and sociological insight of Gidla’s account of caste oppression.

The book’s British and American publishers have promoted it as the untold story of India’s Dalits. This is not a harmless promotional claim. It imposes on Gidla’s book a wholly undue burden of representation, one that would never be applied to, say, a work by a Brahmin writer. It is also untrue. In terms of detail and narrative skill, Gidla’s stands alone, but it is also part of a tradition that includes such writers as Omprakash Valmiki, Narendra Jadhav and Siddalingaiah (to mention only those with memoirs available in English). Another Dalit, Meena Kandasamy, has just been shortlisted for the Women’s Prize for Fiction.

It would be a shame if British readers thought that this book told ‘the Dalit story’ and thus took care of the matter. Dalits are just as underrepesented in publishing as elsewhere, including in what is transmitted from India to the West. To cite just one example, Devanur Mahadeva, widely regarded as one of the greatest modern Indian writers, has scarcely been published in English and never in this country. Ants Among Elephants will, one can still hope, be the book that changes all that.