Genie and Paul is an exploration of identity set in north London

Sharply written and moving, Natasha Soobramanien's debut fuses the familiar and unfamiliar immigrant experience as its unfolding narrative shifts between Mauritius and London.

The plot of Genie and Paul crystallises around 2003's Cyclone Kalunde, a natural disaster that badly affected agriculture on Mauritius. Nasa

Genie and Paul, Natasha Soobramanien's debut, is loosely based on the novel Paul et Virginie by Bernardin de Saint-Pierre, a slice of colonial sentimentality written in 1787 and apparently full of kindly slave masters and charming natives.

Soobramanien transposes the central relationship between Paul and Virginie onto her eponymous protagonists. In the original novel, Paul and Virginie are lovers who are like brother and sister, while Genie and Paul really are brother and sister, sharing the same mother but with different fathers.

They move to London from Mauritius as children and their different relationships to their birth country form complementary poles: for Paul, Mauritius is the Eden of his childhood to which, it turns out, return is always a gesture of self-annihilation; for Genie, it is little more than a place name in a passport. For Genie, Mauritius is a private language (Creole, spoken at home) and a narrative spread thin through multiple retellings; for Paul, it is the object of a homesickness that spreads to poison his adult life, even as he ostensibly forgets Mauritius and stops longing for it.

The novel itself shares aspects of both positions: imbued with an intense sense of place that it brings to bear equally on London and Mauritius, it remains at least initially at a careful distance from the latter, filtering the direct experience of the island through literary representations.

In the context of that vague umbrella term, "the immigrant experience", this feels truthful: one's relationship with a lost homeland is bound to ricochet between indifference and fascination, numbness and pain, because the lost place always leaves a gap that the new home can't entirely fill. The best moments in Genie and Paul are when Soobramanien allows herself to be specific, as in an engaging passage in which Genie sorts her collection of novelty soaps, most of which have lost their smell: "All her efforts at self-control, forbidding herself the pleasure of using these soaps (this thwarted pleasure an odd pleasure in itself), all efforts to preserve the integrity of her collection had proved pointless: having been lumped together in the same basket all these years, they had pretty much come to smell of one another."

A comparable system of categorisation by imaginary attributes haunts the margins of the novel: the colonial and neocolonial hierarchies that have rendered Mauritius a kind of lost zone, full of an incongruous mix of rich international tourists and people so poor they can never leave.

Soobramanien vividly describes the forced deportation of people from the Chagos Islands, made homeless in the early 1970s to make room for a US military base. Not being able to leave, not being able to go back, coming from a place that might as well be nowhere: these are, Soobramanien makes increasingly clear as the book goes on, not just nostalgic literary tropes but real violations inflicted on real people. When an old friend of Paul's asks him if riots in Mauritius were reported in England, Paul experiences a pulse of shame: from the perspective of England, Mauritius barely exists.

It only appears in the global media when affected by suitably global events, and preferably apolitical events like weather: Cyclone Kalunde, for example, the 2003 disaster around which the book's plot crystallises.

Soobramanien deftly describes the experience of returning to a long-lost "home" only to find that one is not fully recognised by those who never left. When Genie goes back to Mauritius for the first time since early childhood to find Paul, she feels compelled to insist to a hotel bartender, who has no reason to care, that she is "not a tourist".

And yet, she acknowledges the assessment of Mauritians, who do not find in her one of their own: "It had been apparent to everyone Genie had met back in Mauritius that she was a foreigner, even before she opened her mouth."

It is different for Paul, of whom Soobramanien tells us a number of times that his skin is "the colour of honey"; it's also Paul who, for the most part, ventriloquises descriptions such as: "Her hair was a shinier blue-black and her blue-brown eyes gleamed in her brown skin." Sickly sweet phrases such as "honey-coloured" (part of a well-known menu of gourmet caste distinctions: chocolate, café au lait) are hard to swallow in this context. Their very sweetness echoes the colonial European view of "backward" nations as childlike and in need of a firm hand.

Genie, however, knows how to make the multiple estrangements of identity into something easy and familiar. Not coincidentally, she is a Londoner: the city is the novel's other beloved place and specialises, like many big cities, in a high-octane alienation against which Genie's rootlessness appears quite mundane.

Throughout Soobramanien describes London with tender attentiveness; as Genie begins her search for Paul, not yet realising he's left for Mauritius, she loses herself in "places so familiar she barely saw them any more ... streets where all kinds of Londoners came together ... places where memories of Paul through the years were layered one over the other". Perhaps all big cities offer this possibility of losing one's lostness, because they are essentially impersonal.

Paul's second return to the island is prompted by an accident: when Genie takes an ecstasy tablet he has given her and becomes seriously ill, he leaves London for Mauritius hoping to expiate his guilt - not just the guilt of having harmed Genie but the larger, more inchoate guilt of having left the island in the first place, though he did so not of his own will and as a child.

The drug experience, with its promise of immediacy and community, stands in for the fantasies of a "natural" life that inspired the novel Paul et Virginie. But this desire can only return as a poison: Genie and Paul's central axiom might read: "You can never go back."

Paul's refusal to accept this loss eventually destroys him; Genie, younger, more flexible and less burdened by memories, avoids his fate by treating the whole concept of home with the practised lightness of the young, urban western European she has become.

Genie and Paul is that well-known phenomenon: a promising first novel.

At times the pace drags and the many different voices have a tendency to blur into the same homiletic tone, but there are moments of brightness throughout and the last third of the book is moving, engaging and sharply written.

The book's flaws can be partly blamed on the dull weight of contemporary anovelistic mores: it is as if a whole generation of writers have been officially tasked with the collective project of interrogating memory and storytelling traditions.

Both are fine subjects as far as they go but, because any narrative is always already an interrogation of memory and storytelling, they are like calorie-free substitutes for the richness of real concerns. Soobramanien really does have the latter, underneath the veneer of convention, and at its best Genie and Paul fuses the familiar and the unfamiliar and strikes out for its own territory.

Hannah Forbes Black is a writer and artist who lives in London. Her work has appeared in The Guardian and Intelligence Squared.