Roberto Saviano: Zero Zero Zero (Allen Lane)

Many others have drawn comparisons between the cocaine trade and traditional capitalism, whether in terms of captive markets, unfettered greed or competitive savagery. Others have described communities and nations debased. As has been said often enough, coke eats away at the rule of law as surely as it destroys nasal membranes. No one has brought Saviano's desperate sense of urgency to the tale.

Simply put, he thinks the world as we know it is at stake. The threat - in truth, it has gone far beyond a threat - is no longer faced only by developing societies glimpsed on the TV news when mass graves are uncovered, or the latest cartel kingpin is run to ground. Saviano is describing an existential battle between a parasite and its host, between an irrepressible multi-billion dollar industry and a planet full of customers demanding to be exploited.

Zero Zero Zero swarms with facts and overflows with insights. Crooked cops, bought judges, murdered journalists, massacres in the streets? This much we know, surely, from all those Godfather movies and the semi-fictions of "true crime" publishing? Saviano has plenty of that, and plenty of tales of violence so disgusting they should make any reader reconsider definitions of terrorism. Then he causes you to pause, almost awestruck, with a string of simple facts.

In 2008, as we all know, global banking stood on the edge of an abyss. For months the most urgent need of international finance was "liquidity". What happened and why it happened are questions involving other stories, though the laundering of massive amounts of drugs money through banks like HSBC played a part. Instead, Saviano refers to Antonio Maria Costa, the head, in 2009, of the United Nations Office on Drugs and Crime.

This individual made what the author describes, reasonably enough, as a shocking statement: "He had been able to ascertain that criminal organisations' earnings were the only liquid investment capital some banks had to keep from failing." In other words, drugs money was propping up the global economy.

Why would it not? Cash profits estimated at $352 billion - a third of global banking's losses in 2009 - have to go somewhere. Two Bogota University economists reckon, indeed, that "97.4 per cent of the revenue from narco-trafficking in Colombia is regularly laundered through banking circuits in the United States and Europe..." It counts as a handy addition to the bottom line for banks rebuilding balance sheets.

Again, why not? A pure capitalist with no scruples might even applaud the transmutation of criminal earnings into mortgages, loans for decent businesses, the bonds raised by governments to build schools, or the banking taxes spent in the name of a better society. Saviano makes a different, no less depressing point.

Drugs are in the world's financial bloodstream. In terms of its social,

economic and political systems, the planet is addicted. The idea that cocaine is a problem confined to the border towns of Mexico is a fiction. Well-informed and sober people who would never dream of touching coke depend on its power to maintain the illusion that the world is a more or less respectable, generally decent and mostly honest place.

This can't last. Saviano admits, in a text that sometimes veers towards the frenetic, that sometimes he wants to scream his message. If seizures alone give a clue to global consumption, the first and most obvious fact is that many more people use cocaine than society is prepared to admit. It is obvious, too, that most consumers do not (or not yet) have the demeanour of addicts. Cokeheads with any degree of self-control are respectable types, often enough professional sorts with responsible jobs.

They don't talk much, after dinner, doing their lines at table or in the bathroom, about the connection between their recreation and private armies, slaughtered villages, corrupted politicians, torture, arbitrary executions or the elevation of psychopaths to positions of which Caligula could never have dreamed.

They will not often pause to think that their little bit of coke has made its contribution to the coffers of actual political terrorists, few of whom refuse the revenue. As to what the drug has done to hopes for democracy on every continent, that probably counts as someone else's problem.

If the trade's profits are (or were) $352 billion, that's a gauge of political power in anyone's language. The fate of Russia since the fall of Communism can be measured, for one example, against the rise of the Russian mafia. Those peculiarly vicious mobsters - in the narco-world, merciless cruelty is your MBA degree - are busy in the cocaine trade, and profiting mightily. Their muscle and their investments ensure that modern Russia suffers no nonsense over the rule of law.

Yet why pretend that Wall Street and the City of London are immune to the effects of $352 billion? England's capital is well-established as one of the planet's centres of money-laundering. What kind of cash is most in need of a rinse and a spin through the system? Or did we allow collective amnesia when a subsidiary of HSBC was fined almost $2 billion - "less than a third of what they'd taken from Mexico alone" - when drugs gangs washed soiled money through their accounts? The United Kingdom, corporate home to "the world's fifth biggest bank", did exactly that.

There are other ways to read Zero Zero Zero. Saviano is unsparing on the human cost of an insidious drug. His portraits of those who run the trade, clever or clownish, blood-stained or scrupulous avoiders of all dirty work, are a journey around one of hell's less-publicised circles.

His descriptions of the smugglers' ingenuity, from the fleets of submarines carrying tons of coke to the liquid cocaine shipped in fruit pulp, consignments of jeans or upholstery fabric, are riveting. To every version, Saviano brings a moral force.

In Italy, Umberto Eco has called the journalist a national hero. This is partly because a previous book, Gomorrah, exposed the Neapolitan gangsters of the Camorra. It is also because of the consequences: since 2006 Saviano, now still only 35, has had to live secretly under police guard because of death threats from one of the clans. His urge to speak truth is therefore unimpeachable. Zero Zero Zero might have imperfections, in construction and tone, but such observations come easily if you have not had to bet your life on your work.

Saviano reaches reluctant conclusions about what that bet has been worth. His personal agonies are real. He also concedes, finally, that all those "wars on drugs" so dear to politicians have been worthless. Market forces, as the pure capitalist might say, have won. The last remaining answer to a pandemic of crime is legalisation.

If you cannot separate people from their drugs, at least keep criminals out of the transaction. It is not a brave thought, but it will do.

Zero Zero Zero by Roberto Saviano is published by Allen Lane, £20