The Indian Clerk, by David Leavitt

Srinivasa Ramanujan was an exceptionally gifted mathematician who died at 32 in 1920. Born in Erode, now the Indian state of Tamil Nadu, Ramanujan was a clerk in a soulless government department, personifying the babu - or the intermediary between the ruler and the ruled that Thomas Macaulay had thought necessary for the British to rule India. Ramanujan was not formally trained in mathematics, but had an intuitive genius for numbers: their rhythm, their interwoven patterns which appear magical, like the score of a symphony, to the one who can see the meaning beyond.

Ramanujan pursued maths as a hobby, and was reaching a dead end in 1913. He began writing to British mathematicians about the zeta function and Riemann series. Only the cricket-loving GH Hardy responded, intrigued to see how Ramanujan was figuring out complex problems with untried techniques. And so began a friendship, the subject of David Leavitt's remarkable novel. Hardy brought Ramanujan to Cambridge, and they worked together for five years. Ramanujan remained shy, vegetarian and steadfastly asexual; his health suffered in First World War Britain, with its absence of fresh vegetables, and he returned home, only to die young.

Ramanujan has fascinated many artists. Last year, Théâtre de Complicité staged the brilliant A Disappearing Number, which wove the notion of prime numbers into an exploration of the purity of an identity. Stephen Fry has planned a film about him. Shobana Jeyasingh's ballet Correspondences also dealt with his life. Leavitt has the exceptional talent of making the abstract and abstruse accessible. He is not shy of using equations early in the novel, but that is not an exasperated surrender to concepts that cannot be translated into plain language. The equation sings and soars, revealing hidden beauty in the pattern; underscoring why mathematics remains an art.

At one level, the Ramanujan story is a fairy tale in which a Westerner recognises an undiscovered talent and seeks to impress the world by displaying that lustre. But the political context cannot be ignored; Leavitt deftly shows how Hardy, the consummate mathematician, is tone-deaf. Leavitt lulls us into a non-political milieu, showing us the repressed homosexuality, the stifling atmosphere of Cambridge's academic halls, and the brilliance and banality of conversation among dons.

Then he springs upon the reader what EH Neville, another Cambridge mathematician who played a crucial role in bringing Ramanujan to Britain, has to say: "India has produced great scientists... poets and philosophers, but there is a subtle tinge of patronage in all commendation of alien literature. Only in mathematics are the standards unassailable". So the "mortal blow" to the assumption of racial superiority "was struck by the hand of Ramanujan".

In the second decade of the 20th century, Britain was the unquestioned global power. India was the jewel in the crown of its empire, but also a possession, a property. Imperial arrogance was at its height. Indians might have invented zero, and Arabs algebra, but the West knew how to prove things with theorems and equations. Here was Ramanujan, a colonial subject, challenging the very notion of colonial supremacy.

In showing Hardy's lack of concern for larger currents, Leavitt also demonstrates his humanity, in thinking beyond barriers of nationality and ethnicity. But he does not ennoble him, for Hardy fails to see Ramanujan's need for warmth. For Hardy, mathematics alone was important, like art for its own sake: the result and its usefulness were not. Yet method mattered, out of the Euclidian necessity of explaining how one reached one's destination.

Leavitt writes that Hardy had never encountered genius that was "wild and incoherent, like a climbing rose". For Ramanujan, the result mattered; how you got there did not. When pushed how he got an answer, he would either go silent, or credit a goddess. For someone as deeply rational and atheist as Hardy, this was blasphemy. This ploy, of playing reason and faith, works delightfully.

His biographer Robert Kanigel called Ramanujan the man who saw infinity. Leavitt puts it beautifully, quoting his fictional Hardy: "For any true mathematician, life is not the thing, but the thing that interferes. A slate and some chalk. That's all you need... A slate and some chalk, and that world – the real world – is yours."