It is much easier to decide what literary genius is in fiction than in non-fiction. To the demanding reader of fiction, literary genius resides for the most part in the experience of surprise, in being disarmed.
We come to a work of fiction sceptical that it can make a world real and meaningful, even essential, for us, and ask to be won over by the writer's vivid and imaginative use of his or her freedom in the realms of language, structure and plot.
But when it comes to narrative non-fiction, the writer is both fulfilled and constrained by his responsibility towards a world that precedes the book and is the reason for its being written.
This limits expectations of the genre and makes its purveyors more dependent than independent.
Indeed, the very techniques and effects that thrill us in fiction and are now increasingly channelled by modern-day long-form reportage, make us suspicious - we wonder if the writer is making some stuff up.
For the work of non-fiction to be good, truthful and solid, we feel it should essentially be duplicatable by another intelligent human being entering the same field. There is no room here for the wilfulness and wizardry of literary genius - truth and invention cannot be simultaneously indulged.
Non-fiction writers, it seems, are either busy bees like David Remnick or smart alecs spinning a grand theory per book or essay, such as Malcolm Gladwell, or else unreliable fabulists, like Ryszard Kapuscinski.
It says something, then, that Beautiful Thing, Sonia Faleiro's portrait of a teenaged Mumbai dancer, Leela, and her bright but brittle world, is so compelling that it invites from us the question of exactly what might constitute genius in non-fiction.
Faleiro's book begins in 2005 with her and Leela talking to each other in Leela's tiny flat in Mira Road, a grotty suburb of Bombay (Faleiro prefers, like some other Bombay writers, the city's old name to "Mumbai"). Their conversation is intimate, but not private - Leela's most favoured "kustomer", the owner of the bar at which she works, lies fast asleep on the bed beside them.
This encounter sets the template for the entire book, in which the most intimate, manipulative, or bruising encounters between women and men are dissected by the book's many subjects (both female and male) in the most candid, matter-of-fact way, and the women live in one long continuous night, often black to them but sometimes also beautiful, in which there hovers, in every frame, the shadow of a man.
Behind Faleiro's protagonist lies a Bombay institution with a storied history - the dance bar.
Now outlawed by the government of Maharashtra, which runs the city, the dance bar was for decades the site and channel of many of the city's pleasures, adding the shimmer and sizzle of glamour, the exuberance and melancholy of Bollywood film songs and a frisson of romance.
By dancing in front of customers in an environment where physical contact was denied, a dance bar girl became an object of desire with a power far greater than her importunate suitors, some of whom would have to throw money and gifts at her for months before she agreed to meet them in private. "They think I dance for them," says Leela, "but really, they dance for me."
Although at first sight no more than an ornate screen for prostitution, the dance bar was also an institution in its own right, with its own codes and rituals.
Crucially, it was viewed by many of the girls who worked there, often after early experiences of abuse in their own homes or in villages where feudal norms prevailed and women were seen as chattel, as a place of refuge, even as a gateway to riches.
The girls, as revealed by Faleiro's enormously detailed description of the psychological landscape of the trade, were likely to view others as queens might commoners.
When they were shut down (we see from the arc of Leela's story), the girls suddenly found themselves independent in the most negative sense of the word and were pitchforked into a sickening world of abasement, desperation and fear.
The book's great achievement lies in its breaking down of the walls between its upper-middle class narrator and her bold yet skittish, cynical yet fragile, subject, and its invention of a language that accommodates the registers of both these voices without either one coming across as contrived. From the very beginning, Faleiro strives to establish a phonetic naturalism that lets us into the world from which Leela and her colleagues come from, giving us, through their vivid monologues, japes, flights of fancy and sneers, "bijniss" for "business", "hotil" for "hotel", "hensum" for "handsome", and "kalass" for "class".
This is not mere mannerism - each time such a word is repeated, we are taken by language from our polished dictionary world into a place foreign to us, and begin to hear in these words layers of meaning specific to the circumstances in which they circulate.
Faleiro is not the first non-fiction writer to discover that the truths of a subculture can be opened up only through a detailed attention to its vocabulary and grammar, but she is certainly among the most skilled.
It is not just the Indian way of pronouncing a word that is replicated, but also the cadences of Indian speech, with its instinct for persistent repetition (among the gifts Leela desires from customers is "a new wardrobe, everything within matching-matching") and its tendency to coax agreement for every assertion by adding a "na?" at the end.
Although it is ostensibly "reported" and therefore not original, in truth the dialogue in Faleiro's book carries a power more earned than inherited, achieving its effects not merely because of the speaking and cursing of its unforgettable characters, but also because of the writer's remarkable ear.
To Leela's gifts for metaphor, Faleiro adds her own. A girl is seen with her silken hair "billowing about like an unpinned dupatta", while Leela's boyfriend, the balding bar owner Purshottam Shetty, makes up for his many shortcomings "by being cooler than a chuski", or ice-cream stick.
These are metaphors rooted in the very world they describe.
Faleiro's book stands alongside Vikram Chandra's novel Sacred Games as the most memorable representation of Mumbai's street language in its literature.
But it also occupies a room of its own for the acuity of its portrayal of the most peculiar kinds of guilt and predation, provocation and neediness, generosity and spite, surreal spectacle and moral reversal.
A bar dancer is raped by her son. We expect her to be unhinged by rage and self-pity but instead she creeps into a corner and comforts herself: "At least he didn't hit me. I'm an ugly face in a glamour line and had he damaged me further I would have been thrown out of the dance bar and forced to become a waiter. The humiliation! Merciful God, you saved me."
It is in the context of such encounters that the story of Leela's own life, racked by violence and its memories, abrasive in its poverty and need, holding no illusions about the nature of desire or power, lusting for material comfort and the highs of intoxicants, is told by Faleiro, all the way down to the fantastic fatalism and unconscious courage revealed by the protagonist in the book's final act.
Beautiful Thing shows how a work of non-fiction may be both journalistically rigorous and brightly novelistic, and places the author alongside writers such as Basharat Peer, Samanth Subramanian (another contributor to these pages), and Siddhartha Deb, at the vanguard of the revolution currently gusting across the landscape of Indian non-fiction.