THE FUGITIVE in question is Joseph Kony - the mad, prolifically murderous leader of the Lord's Resistance Army, a militia of Christian fanatics and their mostly kidnapped legions of under-age fighters, who have been terrorising northern Uganda and surrounding countries for more than 20 years, at the cost of thousands of lives.

The LRA's declared aim is to impose on Uganda the strict rule of the Ten Commandments, although the means that it has employed to reach these ends have taken flagrant liberties with the sixth (thou shalt not kill), eighth (stealing) and ninth (lie), played pretty fast and loose with the first (having no other gods), third (taking God's name in vain) and tenth (coveting), and can claim compliance with the seventh (on committing adultery) only insofar as God is prepared to gaze benignly upon Kony's peculiar domestic arrangements - he has, by some estimations, more than 80 wives, few if any of whom had much say in the matter.

Matthew Green, a young British journalist working the East Africa beat for Reuters, became fascinated by what he read and heard of Kony, as he diligently collated endless incredible, and apparently utterly inexplicable, atrocities perpetrated by the LRA.

With the mixture of curiosity and bravado that animates the best reporters, Green decided in the first half of 2006 that it might be interesting to go to find Kony and ask the warlord what he thought he was doing.

It was hardly a trivial undertaking. Measured against Kony, Osama bin Laden is a model of availability and hospitality, and at the time that Green embarked on his quest, he was reckoned to be in a less jovial mood than usual.

Believed to be seething in his redoubt in southern Sudan, where the LRA is sheltered, supplied and armed by the unlovely regime in Khartoum, he had been indicted by the International Criminal Court in The Hague on 33 counts, including rape, sexual enslavement, unlawful killing, pillage and war crimes, which included the abduction of countless children, stolen in armed raids and conscripted as the shock troops of his crackpot crusade.

Aware that his quest for an interview with Kony was likely to end in failure, Green made the most of the getting there. Winging it across Uganda into Sudan and eventually to the Democratic Republic of Congo, he found people who had known Kony for years, in one capacity or another - school friends, comrade guerrillas, escaped kidnap victims - and his book skilfully employs their recollections to construct Kony's belief-beggaring life story, from poor-born peasant child to faith healer to jungle warrior to a messianic cult leader and mass murderer, a cross between David Koresh and Pol Pot.

Green is also alert to the corruptions - political, financial and moral - that flourish in any war zone. In Gulu, the Ugandan town that serves as a base for journalists, aid workers and others professionally interested in the war against the LRA, the hotel favoured by foreigners is owned by the army officer allegedly leading the hunt for Kony - whose keenness to get his man is therefore debatable.

The situation is not, Green ruefully reflects, as simple as it looked from his office.

“It was,” he writes, “a conflict in which the people who chopped off people's noses were also victims, having been abducted and forced to kill in Kony's name. It was a conflict in which people would give food to the very rebels who could wipe out their whole village, hoping it would help their lost sons and daughters to survive. And it was a conflict in which people felt betrayed by both the rebels who terrorised them and a government who left them to rot in camps.”

It would be doing Green's splendidly spun yarn a disservice to reveal whether he won his meeting with Kony. But the more he delves into the story, the more he realises that Kony is, in the complex power plays that bedevil Africa, less significant than he thought.

The inevitable truth is that the existence of the LRA, and its folk-devil kingpin, suits outside powers nicely - Sudan's spiritual figurehead, Hasan al-Turabi, whom Green met in Khartoum, and Uganda's President Yoweri Museveni, are among those who benefit politically as Kony's rampages terrorise the people they purport to represent.

Green sketches this wider picture well, deploying his inside knowledge at the service of the story, rather than the other way around - a pitfall of journalists' travelogues.

If The Wizard of the Nile has a flaw, it is that, perhaps betraying his background as a hard news reporter, or perhaps simply out of modesty, Green is too reluctant to take centre stage in his own drama, even shrugging off a bout of malaria in a few lines. Anyone who signs up for a journey of this length - although none of the 352 pages feels superfluous - wants to know about their guide, and Green could impose himself a little more.

But this is a minor quibble at a fine, brave book that at its best recalls the vivid reportage of Ryszard Kapuscinski or Nick Danziger, and illuminates a rarely understood part of the world, and even less fathomable extremes of human mendacity.

The Wizard Of The Nile: The Hunt For Africa's Most Wanted by Matthew Green

Portobello, £14.99; 352pp

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