Sometimes the Swedish Academy surprises by making the obvious choice. For all the pre-announcement buzz around the names of Cormac McCarthy and Kenyan Ngugi wa Thiong'o, this year's winner of the Nobel Prize in Literature should have looked a much safer bet than either. For many years, Mario Vargas Llosa has ticked every major box for Nobel eligibility - except, perhaps, one.

His varied and prolific output as a novelist has confronted with panache and audacity almost every significant challenge in the literary and social life of his place and time.

The exact opposite of an ivory-tower aesthete, he plunged into the bruising realities of politics and power: an immersion that took him to the threshold of the presidency in Peru. Given that Alfred Nobel's famously gnomic legacy stipulates that the literature award should go to a writer who exhibits an "ideal tendency" - usually interpreted as a social conscience in some guise - as well as virtuosity of language and form, no novelist could have done more to bridge the gulf between his words and his world.

So why will some observers still find Vargas Llosa a divisive choice? Because his elevation so clearly upends the idea - popular among United States critics of the prize - that the Nobel always goes to fashionable leftist scribes. Remarkably, this delusion persists in the face of striking evidence to the contrary. Recall that the great conservative curmudgeon, V. S. Naipaul, won just weeks after September 11, 2001.

In Vargas Llosa we probably have the first non-British Nobel laureate who has expressed his admiration for Margaret Thatcher. But it would be wrong to label his presidential campaign in Peru in 1990 - he lost against crooked populist Alberto Fujimori - as right-wing in any straightforward sense. He stood on a classic liberal (not merely "neo-liberal") platform for liberty, the rule of law, and free enterprise controlled by transparent institutions of the state.

In Europe, the centrist stance would have appeared banal. In Peru, it looked almost quixotic. And yet he was hobbled in the end by his Achilles' heel: the perception that this patrician intellectual had insufficient sympathy for the Indian masses of his continent.

From his tremendous debut, The Time of the Hero (1963), driven by his own miserable years as a teenager from a broken family at Lima's military academy, Vargas Llosa's fiction has anatomised the corruptions of power and the drama of those mavericks or visionaries who rebel against it. The Nobel citation refers to "his trenchant images of the individual's resistance, revolt and defeat".

In common with almost every important writer of his generation (born in 1936), Vargas Llosa's coming of age in politics and literature involved a twin embrace of avant-garde ways of writing and of an anti-authoritarian politics that took aim at the cruelty and hypocrisy of moribund Latin American institutions: the church, the military, the patriarchal family, the plutocratic elite. Yet, with mischief, fantasy and passion, his books led him more in a libertarian than a revolutionary direction.

When Vargas Llosa punched his old friend Gabriel Garcia Marquez during a row in Mexico City in 1975, there might have been some personal reason behind the brawl. But their dramatic falling-out also signalled an ideological parting of the ways.

Whatever their similarities as irrepressible storytellers, Marquez had kept faith with Castro and the Cuban Revolution: always the final touchstone of commitment in Latin America.

Vargas Llosa broke decisively with Fidel, especially after the trial of the dissident poet Heberto Padilla in 1971. Some foes, both political and literary, have never quite forgiven him.

The 1970s also saw a new irreverence enter his fiction. Most famously, Aunt Julia and the Scriptwriter (1977) played mind-bending games with the corny conventions of the soap opera as it offered a fantastic version of his own eight-year marriage (from the age of 19) to Julia Urquidi, his uncle's sister-in-law.

It might be fair to say that high comedy, pop-culture pizzazz and frisky eroticism all tend to be in short supply among recent winners of the Nobel prize. Vargas Llosa does much to plug those gaps.

Yet his efforts to capture his region in colourful, big-picture novels of politics and history never ceased. The War of the End of the World (1980) unfolds among utopian rebels in 19th-century Brazil but in effect explores the pitfalls of revolutionary struggle now as well as then. Peru's own agony with the guerrillas of the Shining Path - who turned the grievances of the poor and landless into the vehicle for vicious terrorist attacks - fed into semi-documentary novels such as Death in the Andes (1993).

For his critics, such works indicate that Vargas Llosa has never really "got" the depth of suffering and injustice among the Indians.

What he gets, with brilliant intensity, is the battle between conformity and conscience. The Feast of the Goat (2000) - his novel about the Trujillo dictatorship in the Dominican Republic - surely counts as one of the past half-century's finest fictional investigations of tyranny and resistance. In its colour, craft and sheer suspense, it also shows that the Swedish Academy has managed to pick one of the most gripping narrators in modern Nobel history.

- Independent