The banana has to be the most absurd and obscene of fruits  though in fact it's not officially a fruit but a herbaceous plant. After you've unzipped one, what do you do with those sad, limp strips of skin? It is always banana peel that causes ludicrous falls, never apple cores or cherry stones. And then, having bared the pulpy prong, how can you consume it without blushing? In the early 20th century, only loose women dared to eat bananas in a public place. Nowadays, the banana has become banal. Boringly available all year, it looks and tastes standardised, and could almost be the result of mass production in a factory: since it duplicates itself through rhizomes rather than scattering seeds, it is, as Rich Cohen points out, always and everywhere the same, like Coca-Cola or Heinz baked beans.

The history of the banana business, however, has its sensational side, dabbling in assassination, revolution and the skulduggery of international finance. The countries where the plants grew may, as American importers scornfully said, have been "banana republics", but they all bowed down to the man they nicknamed the Banana King  the cranky, ruthless Sam Zemurray, the subject of Cohen's biography, who as president of United Fruit made his company "as ubiquitous as Google and as feared as Halliburton", rapaciously representing the US in those equatorial latitudes that Pablo Neruda, in a poem attacking the banana trade, called "America's sweet waist".

Zemurray had what Cohen considers to be an allegorical American life. He arrived in New York from Moldavia in 1892 at the age of 14, uneducated and penniless. Before long he was grubbing together a small fortune by rescuing metal scraps from dumps and selling them; expert at making waste turn a profit, he bought up bruised bananas in the Alabama port of Mobile and with the help of train drivers and telegraph operators sped them to inland grocers before they blackened. "He was," says Cohen with a mock-heroic flourish, "a kind of existentialist, skirting the line between wealth and oblivion, health and rot": imagine Sartre manning a market stall.

The result was a commercial empire, based in New Orleans, which came to control the political destiny of those benighted republics below the American belt and made Zemurray a sly, unlicensed agent of Washington DC's foreign policy. His plantations were situated in areas of insurgency, described by Che Guevara as "dominions of United Fruit". He therefore helped engineer an uprising in Honduras, and allowed the CIA to use his banana boats for gun-running. Cohen also suspects him of covert involvement in the Bay of Pigs invasion. Back in Louisiana, he was briefly inconvenienced by the populist campaign of governor Huey Long; when Long was killed, Zemurray may have quietly smirked. Those who refused his offers often ended up dead. He was, as Cohen puts it in another jocularly epic tag, a "Don Corleone of the isthmus".

Zemurray began as a piratical privateer, but ended as a fixer in a new world carved up between global corporations. Wealth gave him power, and he struggled and fumbled as he tried, like the newly imperial US, to use it righteously. On the face of it, he was as unlovable as any other capitalist bogey, but Cohen nurtures a sneaking regard for the man, mainly because his success was achieved at the cost of the snooty Wasps who despised Jews, Catholics and the rest of the huddled ethnic masses. Imagining Zemurray's thick accent, Cohen says he must have had "the Yiddish-inflected voice of our grandparents, the fruit pedlars, the street hagglers". They're not my ancestors, but I found the story riveting, mainly because of the mischievous ease with which Cohen tells it. He has done his research, but he's no prissy, footnote-addled academic. "I'm not sure where he lived," he shrugs after attempting to locate Zemurray's home in Mobile. "I've not been able to find the original document," he remarks elsewhere with equal nonchalance. Who cares? Beneath the comedy, Cohen is a cosmic nihilist, for whom "the world is a succession of fortunes made and lost, lessons learned and forgotten", so in the end nothing much matters.

Documentary veracity counts for less than the dashing energy of Cohen's characterisation, and the moody atmosphere of the landscapes in which he sets this buccaneering life  New Orleans with its malarial damp, the jungle in Panama where an incomplete, unbuildable highway is "defeated by nature and walks away muttering". Best of all is his horrified contemplation of the monstrous banana in its native habitat, with its leaves shaped like elephant ears and "coiled like a roll of dollar bills". After a tropical downpour you can hear the plants stealthily growing at the rate of an inch an hour as the foliage drips: it is the sound of money being made.