`my gut is shot. I have been sick so many times. The way you do when you travel to dirty places - it's no big deal or anything - but my resistance to that kind of stuff is down. Touch wood, I've been lucky. I've got a lot of friends, international journalists of one kind or another, who got malaria and dengue and things like that. I've missed the horrendous stuff, but I've done my time in the bathrooms of the world."

So P.J. O'Rourke's next book is likely to be a home-grown affair, "a bit of American history in microcosm," where the microcosm is his under-achieving home town of Toledo, Ohio. "The idea is to look at all that has happened in America through the keyhole of this silly, unsuccessful, rather unattractive place. I may change my mind, but that's what I'm thinking at the moment."

In the meantime, he's touring some of the world's better bathrooms to promote the fruits of his most recent round-the-world gutwrencher. Eat the Rich is a treatise on economics, researched in Albania, Cuba, Tanzania and Russia, among other places, and bearing as its title the sort of slogan he would have used without irony a quarter of a century ago, when he was the long-haired, left-leaning, dope-smoking anti-war activist he now loathes with every fibre of his being.

One of the pleasant surprises of the book is that despite all his exposure to the condition of the contemporary world, O'Rourke can still be shocked about it. In Albania, chosen as an example of "bad capitalism", he was appalled by the anarchy that followed the collapse, first of communism and then of the pyramid-scheme craze that mysteriously swept the country. In the book, he writes: "Estimates of the number of weapons loose in Albania ranged as high as 1.5 million . . . the National Commercial Bank in the city of Gjirokaster was robbed with a tank."

But it's in the small incidents that you get the flavour of the place. The chapter on Albania ends with a description of a scene in a cafe, where a local family sits next to him, a four-year-old girl bouncing on her father's knee. "The girl dragged the cigarette from between her father's lips and tried a puff. Mom and Dad laughed. Dad took the cigarette back. Then he pulled a pack of Marlboros from his shirt packet, offered a fresh cigarette to the girl and gave her a light."

Smoking cigarettes himself (the trademark cigar is gone since his wife developed an aversion to the smell while pregnant with their now one-year-old daughter) in Dublin's Shelbourne Hotel, O'Rourke is not unconscious of the irony. Even for a champion of personal freedom, Albania was just a little bit too free.

But much as he disliked Albania, it was nothing to his hatred of Cuba, and one aspect of Cuba in particular. "The prostitution was really gross. I'm no prude or innocent about that kind of stuff, but the desperate edge to prostitution in Cuba, and the obvious involvement of young girls who clearly weren't . . . I don't know if there's such a thing as a prostitute type, but they weren't hard girls. They were kids." The other thing that hardened his attitude was talking to Catholic charity workers in hospitals and other places. "These were not right-wingers or ideologues, or the kind of exiles who hang out in Miami. Theirs was a moral resistance to Castro rather than a political one, and they were appalled by the situation in Cuba." He can be as cynical as ever when discussing the place ("There were signs everywhere saying `Socialism or Death'. After a few days, I was leaning toward the latter option.") But he admits he was more sensitive than normal on that trip because his wife went with him: "She'd travelled, but she'd never been to any place as desperate as Cuba and she was shocked . . . and since I've been covering this stuff for a long time, I might not have been so shocked if she hadn't come along. She pointed out things that I might have shrugged off, but she wasn't going to shrug them off so easily."

It wasn't all harrowing, of course. Eat the Rich is a study of economic success as well as failure and the search for the happy medium took him to places like Sweden (the book's example of "good socialism") too. All the horrors in Sweden were food ("not good, unless you like your reindeer tongue") and his first impression of the country was that there were no "crazy people" on the streets. Then he realised that, like everything in the country, madness was fairly distributed: "Everybody in Sweden is just a little bit crazy."

With an eye on Viking history, O'Rourke concludes in the book that: "Otherwise a marvellously honest people, the Swedes have a blind spot about taking property that isn't theirs, so long as the loot is equally divided." He imagines the conversation on a homecoming longboat: "Yah. We pillaged Ireland. Good. But Sven had seven rapes and Nils had only one. So we all get to rape Sven."

A regular visitor to Ireland, this was his first trip since the economic "miracle". It doesn't feature in the book, but he has a ready explanation for recent Irish success: "It's pretty basic. You had a country that had never been industrialised, with low prices, a high level of education and low wage rates. That's a recipe for high-tech."

O'Rourke's forebears bailed out of here during the Famine (which, characteristically, he blames on trade restrictions rather than the Whigs' laissez-faire economics), and somewhere along the line became "the world's only Protestant O'Rourkes". He explains: "My father's mother died and my grandfather remarried, to a woman who was . . . I think the phrase `barking mad' might cover it. But he couldn't get an annulment, so he broke with the Church and divorced her." No comparison with the Kennedys, then? "No. They've got a vending machine for annulments. There's an 800 number they can ring."

The Clintons seem to have overtaken the Kennedys as the liberals O'Rourke most loves to hate, although trainspotting book readers may notice that a joke about "the thoughts of Lenin" in the paperback version of Eat the Rich is "the thoughts of Senator Edward Kennedy" in the hardback. The subject of Bill Clinton has gone beyond a joke, however. Speaking before the committee hearings that again seem to have shortened the odds on impeachment, O'Rourke mused: "In 50 years' time, people will write very interesting sociology dissertations on why he survived. America can be a morally very sloppy country. It can rise to great heights when it has to, but when it doesn't have to, it can sink to great depths. It has always been that way. I mean, how can a country so nobly conceived have countenanced slavery for so long? It's the problem of being a large, diverse country with no innate national identity."

The Clinton saga aside, he is sure that far more Irish-Americans vote Republican - as he does - than would admit it in public. On a visit to Wall Street ("good capitalism") even he was surprised to find that, far from being a WASP colony, the traders were predominantly Jewish, Italian, "and most prominently of all, Irish". The reason was simple. "They were cheap labour," an Irish trader told him - clerks and runners who learned the trade from the bottom, and climbed.

As luck would have it, while O'Rourke was holding forth in the Shelbourne Hotel, a march to welcome asylum-seekers was making its way around St Stephen's Green. The right-wing author guessed he had little in common with the marchers (and right enough, many of them would be closer to O'Rourke-circa-1970) but on this issue he's right behind them. Work-seeking immigrants are a huge asset to a country ("that's how Britain got good food - before that they boiled everything"), legal or otherwise, he says.

"The difficulty for a country like Ireland - because you have relatively generous social benefits - is that people at entry level cost you more in tax expenditure than they contribute in tax take. That's one good reason for lower benefits, but then there are many good reasons for keeping them high. It's a bitch! But the great thing about being a journalist - or an economist, for that matter - is you don't have to solve problems. You only have to identify them."

Another unsolved problem is religion. In the book, O'Rourke gleefully finds the 10th commandment ("Thou shalt not covet thy neighbour's goods" or "Don't envy your buddy's cow. Get your own cow," as he interprets it) a charter for property rights and the free market. But if the Old Testament is republican, the New Testament has obvious democrat leanings and, pressed about Christ's advice to the man with two coats, O'Rourke admits he hasn't thought much about it.

And yet he is a practising Christian, if "a little on the vague side". Asked if he has any heroes, he says no, although he admired Margaret Thatcher ("from afar, which I know is always easier"). Then he adds: "This Pope's a pretty good guy. I think he's been a stand-up guy who's stuck to his guns. And oddly enough, speaking as the world's vaguest Protestant, I like his stand on moral issues."

Vatican II almost destroyed the Catholic Church, he believes. "The moral evolution of a religion, where we try to figure out what it is God wants us to do, is not something that should be done by a committee. It's not Tony Blair's New Labour. And Vatican II came very close to rubbishing the Catholic Church: not because any one change was wrong, but because all the changes were made very quickly, and on slim evidence. I think John Paul II was a sea-anchor on a Church that was moving too fast. I mean, look what's happened to the mainstream Protestant churches in Britain and America. They've become silly and frivolous - nobody goes to them any more. And the people attracted to them are not exactly the best and brightest in society. They've just become fussy, silly clubs, without any real influence in the world." Although O'Rourke largely bypasses religion in the book, he does grapple with some very abstract problems. Fans will be relieved to know, however, that even in the bleakest of economic badlands, his humour never deserts him. Take his explanation of Ricardo's Law of Comparative Advantage, for example.

Named after the English economist David Ricardo (1772-1823), this postulates that if one person can do X better than he can do Z, while another person can do Z better than he can do X - but can also do both X and Z better than the first person - society should not encourage the second person to do both things. The individuals concerned, and society in general, will benefit more if each person concentrates on what he does best. This is a complex theory, but O'Rourke illustrates it with an example which assumes, for the sake of argument, "that one legal thriller is equal to one pop song as a Benefit to Society (one thriller or one song = one unit of BS)".

He continues: "John Grisham is a better writer than Courtney Love. John Grisham is also (assuming he plays the kazoo, or comb and waxpaper or something) a better musician than Courtney Love. Say John Grisham is 100 times the writer Courtney Love is, and say he's 10 times the musician. Then say John Grisham can write 100 legal thrillers in a year (I'll bet he can) or compose 50 songs. This would mean Courtney Love could write either one thriller or compose five songs in the same period."

Cutting a long example short, O'Rourke proves that if Grisham and Love divide their time between thrillers and songs, the net result would be 78 units of BS (the reference to cattle manure is an obvious bonus). But: "If John Grisham spends 100 per cent of his time inventing dumb adventures for two-dimensional characters and Courtney Love spends 100 per cent of her time calling cats, the result will be 100 thrillers and five songs, for a total Benefit to Society of 105."

He concludes: "The Japanese make better CD players than we do and they may be able to make better pop music, but we both profit by buying our CDs from Sony and letting Courtney Love tour Japan. And if she stays there, America has a definite advantage."

Relentless smartass that he is, O'Rourke still worries about hurting people's feelings (not Courtney Love's, obviously): "The idea is to aim humour at folly, not at suffering. But one's aim is not always true." And although he's never short of an opinion, he has a streak of humility too, which the study of economics seems to have widened: "Economics was like love: the more I learned the less I understood." He is even disinclined now to lay down laws about forced redistribution of wealth, save to say that the record of idealistic government isn't good.

"I don't have strong opinions about the size of welfare benefits; I think it's something each society has to decide for itself. The only thing that economics teaches us about transfer of wealth, about equality, is that there's a price attached. And we have to have our eyes open about it because that price will be charged. There's a price to economic inequality too, as we well know. Especially in America: it's called crack-dealing and a murder rate that's right up there with Tadjikistan."

He sums up: "The trick is to create a happy society, but what works in one society doesn't necessarily work in another. The Swedes have a very uniform distribution of wealth, but there are only eight million Swedes and they're all alike. So, easy for them to do. Try that with 250 million Americans, all of whom loathe each other, and it probably wouldn't work so well."