Now a sprightly 72, the seemingly evergreen Paul Theroux has the kind of familiarity with, and abiding interest in Africa that makes his accounts of travels through that continent somehow different from many of his other travel books.

When he first started travel-writing well over thirty years ago, he was typically finding his bemused way in books like The Great Railway Bazaar (Paddington Station to India) or The Old Patgonian Express (Boston by train to the foot of South America).

Indeed such could also be said about The Pillars of Hercules, which recalled his travels around the Mediterranean (off-season) and The Kingdom By the Sea, which detailed his journey around the coast of Britain. All the time in such travelogues, he was a neophyte, wet behind the ears in terms of local knowledge, meeting quizzical, informative characters in train carriages and at stations, hotels and restaurants.

Typically, he would draw neat, if occasionally amusing, exaggerated conclusions about national character based on conversations with voluble Indians or talkative South Americans. There was clearly a fair amount of colour writing and the novelist’s skill was busily deployed - and why not indeed, as Theroux is the author of many novels.

Africa is different, he knows the score quite well. Some fifty years ago, he worked as a teacher in Malawi for a six-year period. Twelve years ago he travelled down the East side of Africa for a book called Dark Star Safari. Africa tends to draw out in him a journalistic sense of enquiry, a testing of prior assumptions against current evidence.

In The Last Train to Zona Verde - Overland from Cape Town to Angola, the year is 2011, and Theroux gladly turns his back on home in Cape Cod, where the news is abuzz with financial meltdown and bank catastrophe. He blithely bids adieu to vacuous dinner party conversation, internet and email nonsense,  publishers’ deadlines.

“Happy again, back in Africa, the kingdom of light, I was stamping a new path, on foot in this ancient landscape…” the author writes on the first page. “ An ageing traveller now, I took my morning pills, two different ones to keep gout away, a vitamin, and a dose of malaria supressant,” he tells us at the beginning of chapter two.

This time around, he travels up the West side, beginning at Cape Town, a city he loves. There is no escaping the vast disparity in wealth and health in that topograhically open megapolis where all areas of the city - from villa-and-vineyard belt, to township and hovel - are in plain sight, each to the other (generally n the middle distance, presumably.)

He eats fish and chips near the railway station and notices a group of young teenage black boys looking at him. One of them approaches him and hesitantly asks, “Can I finish? “ Having received the writer’s reflexive, unthinking assent, the teenager takes the remaining chips and walks away, batting off the birds. The often acerbic, instinctively sceptical Theroux is blind-sided by the encounter, and feels an unexpected welling up of “helpless pity.”

While there may be a certain sense of return to an old haunt, he has never travelled before through the places he visits on this 2,500 mile journey through South Africa, Namibia, Botswana and Angola. So it is very much a journey of fresh discovery too.

And he does have certain preconceptions challenged, notably about foreign aid. "My first impression of Namibia... was of a place that did not need anyone from outside the country to tell the people how to live their lives," he writes. But in the more deprived, disorderly north of the country, he realises that this was a "snap judgment."

Foreign aid that works independent of governments can be a fine model he discovers, citing the existence of a Texan foundation that is funding a valuable cultural heritage project in Northern Namibia.

But, if you're talking foreigners, he has mostly contempt for Madonna, who adopted an African child, and for Angelina Jolie who chose to have her baby in a private hospital in Namibia. He sees such decisions as cynical image-adjusting efforts, elaborate PR stunts.

Bono too gets a good kicking for telling a journalist that a song called Shoot the Boer was folk music. “So anyone who believed, with Bono, that Malamea’s song, Shoot the Boer was no more than a harmless bit of folklore, and encouraged it to be sung like an Irish ditty, seemed to me an accessory to such assaults.”

Given the fact that he once was a teacher in Africa, the writer has a keen interest in how young Namibian schoolchildren are doing. But that is a slightly earnest, if informative passage, it has to be said. There is much more diversion to be had elsewhere, not least in Theroux’s engaging depictions of the landscape. “Sundown at Springbok was an unexpected and eerie arrival at a twilit town surrounded by rock, with smallish, stucco-walled houses embedded in the slopes of a valley of broken granite." Theroux is a master of travel-writing, long may he roll.

Paddy Kehoe