NOTHING'S SACRED. That's the way I LIKE IT

Shriver knows this, she says, because she has seen it for herself. For almost 12 years the novelist, who is from North Carolina, lived in Belfast, working as a reporter for various American newspapers. She watched as Sinn Fein maintained the illusion that it had no links with the terrorists while reaping the benefits of the bombs. The terror group in The New Republic does exactly the same thing and Shriver's point is that this is what happens: terrorists get what they want. "Zealots have the advantage," says one of the characters. "They never get tired."

It's where this hard truth about terrorism leads that really troubles Shriver. Another of the characters in The New Republic puts it this way: "the terrorists of today are the town-square monuments of tomorrow", a perspective Shriver says was also influenced by her time in Belfast.

"I'm illustrating with I hope not too heavy a hand," she says, "that terrorism is nefariously effective, which is heavily informed by my experience in Northern Ireland. If you know anything about that story, you'll know how handsomely the armed struggle – so-called – paid off for the Provisionals. They are running the place now."

Talking by telephone from her London home, as Shriver says "running the place" her voice rises as if she's slightly losing control of the sentence and it's anger that's doing it. I ask her if it upsets her that Sinn Fein's Martin McGuinness now wields power at Stormont. "It does upset me," she says. "It upsets me fantastically. He shouldn't have been in a position of authority and influence and respect. Sinn Fein has not suffered from what they did at all – to the contrary, they shut out their non-violent competitors; the SDLP hardly exists."

Shriver, who is 54, calls this perspective "realistic cynicism". Others – particularly some of the reviewers of The New Republic in America – have suggested alternative words: amoral, evil even. One reviewer in particular, in New York, where it's understandable that terrorism is still a touchy subject, called the book ghastly and used the phrase "comic novel about terrorism" as if that should tell you everything you need to know.

Shriver's defence against this is that we should be free to use humour around any subject, provided the joke is funny and the timing is right. Finding a way to laugh at terrorism, she says, even after a terrible event like 9/11, is politically important; it's our reassertion of a sense of normal, what she calls a repossession of our world. "After all," she says, "we live in a largely secular world where nothing is sacred, and that's the way I like it."

The problem for Shriver is that others don't see it that way, which is one of the reasons The New Republic is only being published now. It was written in 1998, just before We Need To Talk About Kevin, but at first there was no interest from publishers. Then 9/11 happened and what had been seen as an irrelevant subject was suddenly far too relevant.

"At that point, it wouldn't have been cool to publish The New Republic," says Shriver. "First off, it would've seemed like jumping on the bandwagon, which doesn't suit me; but more importantly, it's meant to be funny and it was in danger of seeming in poor taste. I took a gamble that publishing it now we're not quite so touchy."

And so here it is, 14 years after it was written: the story of an American journalist, Edgar Kellogg, who is sent to Portugal to cover a terror group fighting for southern independence and ends up obsessed with his predecessor, Barrington Saddler, and Saddler's lover Nicola Tremaine. The terror group is led by a charismatic young buck called Tomas Verdade, a terrorist/freedom fighter with the iconographic potential of Che Guevara. He is said to have huge tawny eyes and an appeal that is fundamentally sexual – to women and men.

Even as you read that description, you know it's Shriver being deliberately spiky again, but she's only saying what feels real: to some, terrorists and criminals are sexually attractive. The Norwegian extremist Anders Breivik is probably getting marriage proposals right now and Shriver's killer in We Need To Talk About Kevin certainly would have.

"Absolutely," says Shriver. "There's a level on which we tend to admire people who break the rules and, besides, we are living in a culture that values celebrity above all. There's no distinction made culturally between fame and notoriety. And there's a lot more frisson attached to people who commit acts of wickedness."

In fact, Shriver goes further and suggests that people like her character Verdade might commit terrible acts not because of the political objectives, but for a much more disturbing reason: because of the thrill.

"That's one of the things that drives people to do it," she says. "It's much more exciting to be a terrorist than deliver for DHL, and what drives people to do this is more existential than political. This is universal. It's not just Northern Ireland or Israel or the Tamil Tigers; it's also Islamic terrorism and, for that matter, school shooters. They're all looking to be the centre of attention and want a kind of regard.

"That's what I'm saying about all these people. They want to be important, they want to be noticed, they want their problems to be noticed, but most of all they want people talking about them, they want people poring over their history and worrying about what drove them to this, and they want their opinions broadcast. With Breivik it's working a treat and it's the same with these kids who shoot up their schools."

Shriver argues that this craving for publicity puts a responsibility on journalists – one she believes they are not fulfilling. "I think we should restrain ourselves more," she says. "I don't believe in press censorship and I certainly think that when something bad happens, the facts should be delivered, but that's not all we do, is it? We wallow in it and do all these panel shows and long features and all the op-eds and hanky-twisting about where we went wrong."

Perhaps the reason Shriver recognises this hanky twisting is she did her fair share of it herself after the success of We Need To Talk About Kevin. For some time after that book was published in 2003, whenever a high-school pupil went on the rampage with a gun, Shriver was invited to write features or appear on news programmes to explain why – and for a while she said yes.

"One of the only things I ever said on these programmes was: look, the main reason people do this is to get this kind of attention that we are giving them now and sometimes that attention is so alluring in the culprit's mind that they are willing to get it posthumously." Now, Shriver says no to all those offers. "Yeah, in my sad, small, pathetic way I have finally put my foot down on going on TV news shows every time some kid shoots up his school," she says. "I say no every time – unfortunately, they just get somebody else."

As for We Need To Talk About Kevin, Shriver says she still likes it. But she also thinks some of the millions of people who liked that book, or perhaps watched the film adaptation starring Tilda Swinton, might be bewildered by the political satire of The New Republic.

"The odd thing I've discovered," she says, "is that The New Republic is far more appealing to men than women. It's not only that it's written from a man's point of view but there is something about the subject it's dealing with that appeals more to men. Men seem to get it more, get the allegory, the politics. I don't want to slag women off but I'm sorry – if you're reading this book mostly to find out if Edgar and Nicola get together, you might as well put it down and read something else."

The New Republic by Lionel Shriver is published by HarperCollins, priced £14.99.