Donna Tartt’s first novel, The Secret History (1992), is about a cabal of highly educated classics students at an elite New England liberal arts college who gather around a cold, charismatic classics tutor called Julian Morrow. They are neurotically withdrawn, isolated and contemptuous of the mundane preoccupations of their fellow students (rather like the murderous students in Hitchcock’s Rope). One night, in a kind of Bacchanalian frenzy and as a spontaneous expression of a belief in their own superiority, they murder a local farmer. This is soon followed by the more calculated murder of one of their own inner circle, Bunny, who has discovered, and is appalled by, the truth of what happened to the farmer. The murder of Bunny is an attempt to transcend conventional morality, an act of true Nietzschean pitilessness and indifference. This is the central crisis of the novel, from which all else flows: insomnia, alcoholism, madness and suicide.

The novel, a worldwide bestseller, is narrated in retrospect by one of the student-murderers, a lonely dreamer called Richard Papen, whose conscience has forced him repeatedly to relive the events of that one terrible evening. His guilt at what happened, we understand, has destroyed him. “I suppose at one time in my life I might have had any number of stories, but now there is no other. This is the only story I will ever be able to tell.”

As a Californian, Papen feels himself to be a stranger to the east coast, the setting for the story, at once accepted by his more socially adept friends but destined to remain for ever at a distance from them. His regretful, ruminative voice consciously echoes Nick Carraway’s in The Great Gatsby, and there is, too, in his recreation of mood and atmosphere, and in the slow accumulation of detail, a fey nostalgia that owes much to Brideshead Revisited. But The Secret History is, in truth, for all the great claims made about it, essentially an extremely accomplished realist novel. Tartt takes few risks, if any, with form. Little is left unexplained. Her individual sentences are seldom memorable. Her first-person narrative is melodramatic and marred by static set pieces and great blocks of talk, as the characters mechanically relay important events that have taken place beyond the gaze of Richard Papen. Yet, from the opening paragraph, you are drawn relentlessly into a world of concealment, betrayal and repressed sexuality. It is a seductive world, at once morbid yet true, hysterical yet convincing. For Tartt knows that the obsessive study of the higher humanities seldom humanises; instead, it can create its own peculiar darkness and pathology.

Since the publication of The Secret History little has been heard of Tartt, though there has been a great deal of gossip surrounding her. Although the rights were expensively purchased by a major Hollywood studio, the film of her novel was never made. In the period during which she withdrew into affluent seclusion, publishing only the occasional story in the New Yorker and not much else, it was widely thought that Tartt, like Richard Papen, had only one story to tell. And she had already told it. Was she then destined, like Harper Lee (To Kill a Mockingbird), Ralph Ellison (In Invisible Man) and Henry Roth (Call It Sleep) before her, to disappear into disturbed anonymity?

As we now know, Donna Tartt has spent much of the last decade completing another novel, which is being published simultaneously in Europe and the United States. The Little Friend (which is thought to have earned her [pounds sterling]4m in advance rights sales) is set in 1970s Mississippi, where the author grew up, and opens, like The Secret History, with a startling prologue about the mysterious death of a small boy who is found hanged from a tree. But the novel is not really about the tragedy of the boy; it is more about his younger sister, Harriet, and her struggles to understand the secret sadness of her family. Hers is a tainted environment, one of shabby gentility, of private schools, proms and prayer meetings, and long languid summer nights, the counterpoint to which is criminality and racial exclusion.

The novel is presided over by Harriet’s formidable grandmother and three great-aunts. Perfumed, powdered and prim, these melodiously named southern belles (Edith, Libby, Tattycorum and Adelaide) belong to a distant age of order and elitism. They are part of the southern aristocracy, a defeated people, who nurture a wounded superiority. Their former ancestral home, Tribulation (a latter-day version of Margaret Mitchell’s Tara), survived the civil war, but not the reforms of the civil rights movement. While this, then, is a tale of three generations, it is also about three classes: high-born whites, poor whites, and the black descendants of liberated slaves.

Harriet herself lives in a large, dishevelled house, full of ghostly echoes and reverberations. Its slow, A inevitable deterioration mirrors that of her mother, who never stops mourning her dead son, and her fragile, listless sister, who drifts sleepily through each day. Harriet is an overfamiliar literary archetype: the solitary, inquisitive, bookish child who, through trauma and neglect, is hastened from innocence into experience, creating her own world of fantasy and blighted romance. She is at once knowing and naive, and we have encountered her like many times before, in Henry James’s What Maisie Knew, in To Kill a Mockingbird, in The Go-Between and, most recently, in Ian McEwan’s Atonement.

Harriet desires not only knowledge, but revenge. She never questions her conviction that a poor white youth, who used to be her brother’s friend, was the killer. Nor does she doubt her right to murder him. Like the students in The Secret History, Harriet believes in her own omnipotence and simplistic moral code, which is informed by the adventure stories she reads and by the superstitions and biblical hysterics of the American South. At all times. Harriet cultivates a kind of wilful blindness: in her immaturity and arrogance, she misreads everything. Yet she will eventually learn something far more profound about the cruelty and injustice of the adult world, and begin to understand, too, something of the corruption and fraudulent gentility of the American South itself. So this, after all, like so much fiction from the South, is a novel about inherited guilt, about class, prejudice and hypocrisy, in which even the black housekeeper despises the local “white trash”, who in turn despise all “niggers”.

Martin Amis once wrote that all American writers of ambition were trying to write a novel called USA. What he meant, I think, is that the mission of the American writer, certainly in the latter decades of the 20th century, has been to write, if not the Great American Novel, then at least a great American novel, a work that, as Michael Ondaatje said of Don DeLillo’s Underworld, contains multitudes. Where Tartt differs from other contemporary American writers of ambition, such as Jonathan Franzen and David Foster Wallace, is not in the length of her novels (no one would wish them any longer), but in the way she takes the foundation blocks of so much popular fiction—gun battles, drugs, cartoonish caricatures, high-energy action scenes—and uses them to build something entirely her own.

V S Naipaul has said that he cannot understand why readers feel the need “to be drugged by narrative”. The challenge, he thinks, is to create new forms, to find new ways of writing about the modern world. Well, Donna Tartt writes about the modern world and she certainly drugs her readers with narrative. Elaborately structured, astoundingly well-paced, resolutely unexperimental, her fiction satisfies what may well be our hard-wired hunger for narrative, for coherent, dramatic representation of the human story. This may explain why she appeals to people who don’t really enjoy reading, to those who perhaps buy only one or two novels each year. Why, she is big even in Belgium, an honour few writers can claim.

The Little Friend is audacious, implausible and enchanting. As with the best 19th-century novels, it is indulgently expansive, as cluttered and overstuffed as Harriet’s rambling house. At times, one becomes aware of the strain behind the style: the novel has little of the lightness or real fluency of The Secret History. Tartt never hurries. She is not afraid of scenes intended less to further the action than simply to create mood or deepen character. This time, she also resists resolution: the secret history behind this novel remains as elusive to the reader as it does to Harriet; the riddle of her brother’s death is never solved. After more than 500 pages, we have essentially been party to nothing more than a childish prank and a drugs scam, both of which go wrong. Yet there remains something indefinable and ultimately mysterious about this novel, a certain elegiac tone and lingering regret for the passing, if not of youth, then of an innocence that perhaps never existed at all, neither in America nor in th e life and imagination of foolish little Harriet.