Millionaire writer Darren Shan has sold more than 11 million horror books for children. Not surprisingly, his home is full of books and he recently started collecting art. Walking through his house is like visiting a gallery. Production has just started on Cirque du Freak, the film of his first book that stars Salma Hayek and John C Reilly. So far, so glitzy.

But he lives a strange double life, as he explains from his unassuming dormer bungalow in rural Limerick: it's parties, theatre and art auctions when he's in London, then cows and inquisitive agricultural students at home.

Darren, 35, lives in Pallaskenry village, about 20km from Limerick city, with his effervescent girlfriend, 'Bas', aka Helen Basini, 31. The couple met in London when she was working for the War Child charity. A stunning brunette, a few inches taller than boyish-looking Darren, they make a striking couple.

They first got talking when Bas was putting a children's book together for the charity and wanted to ask Darren for a story. "Darren was doing an event in Kingston, so I went along," she says. "He said he'd give me something for the book and we stayed in touched by email. One message happened to be on Valentine's Day, and I put 'PS -- I hope your Valentine's Day is more successful than mine'. A week later we ended up going on a date." She grins at him fondly. "That was six years ago this February."

Bas has just finished a Masters at the University of Limerick and also works with a charity called No Strings, who use puppets to assist teaching in the Third World.

Darren lived in London until he was six and still has the accent to prove it. His mother is a primary school teacher and his dad works in the same school as a janitor. Now, he's lucky enough to own an apartment overlooking the Thames, just beside the London Eye.

As well as writing, Darren is also mad about art and has recently started collecting some pretty impressive pieces. Six tiny Willard Wigan glass sculptures -- Peter Pan, The Last Supper and other scenes -- all set into the eye of a needle, viewed through special microscopes; original Sandman, Krazy Kat and Simpsons comic book art; a rather nice Impressionist painting once owned by Alfred Hitchcock, plus quirky items such as a stuffed and rather frightening-looking fruit bat and an original 1930s film projector.

The bookshelves are heaving with first and limited editions; Roald Dahl and Stephen King. I stare goggle-eyed at their incredible collection of movies, three deep in the custom-built, glass-fronted shelving units -- more than four thousand of them, all shelved by director, labelled with little handwritten stickers.

But Bas isn't impressed. She shows me 'her' room. It's a small space opposite the movie library, with some framed photos of Bas and her friends propped up against the wall, waiting to be hung in a planned extension. No space on the walls you see.

But having a millionaire boyfriend does have its benefits. Darren is taking her to Las Vegas in a few weeks and he recently bought her a brand new Skoda. "I don't drive," Darren says. "So it's not an entirely selfless present." But why not a Jaguar or a Porsche, I ask him? Bas says: "Darren likes the irony of someone so successful driving around in a Skoda and I don't care about cars. I'll take what I'm given."

"I'm not interested in flashing it about," Darren adds. "And with the roads around here..." He gives a deep, fruity laugh.

In the back 'garden' (a huge grassy field) there's a 10-foot high black and gold sculpture of a masked Venetian gondolier. There's also an abstract stone sculpture further down the field.Students from the adjacent agricultural college climb into the garden to look at the sculptures from time from time, but Darren doesn't mind. "Bit of culture," he grins.

So why horror? "I've always loved it," he admits. "It started with horror movies. When I was back in London, I remember watching Dracula on TV. I've wanted to be a writer since I was six. As I got older, that just became more and more of a goal."

Books like Slawter examine the worries facing a teenage boy called Grubbs Grady, who comes from a cursed family of werewolves. So what was Darren like as a teenager? "I got a bit subdued at 14. Normal teenage stuff; self-conscious, quiet, starting to worry about what the world thinks of you. Didn't want to say anything that might be seen as foolish by friends. So that's why a lot of my characters are outsiders. That's how I felt as a teenager -- out of place, awkward."

Darren is adamant that children are not scarred for life by horror books. "They know what they're getting," he says. "Look at the covers: horrible stuff. More gruesome than the books." And he's right. Subtle they ain't -- worms oozing out of eyeballs; werewolves with blood spurting from their mouths; disembodied heads.

As a genre writer, Darren isn't concerned with winning awards, and doesn't have as many gongs as other Irish children's writers, such as Kate Thompson and Eoin Colfer. However, he was shortlisted for the Irish book Awards in 2007 and has won many teen or kids' choice awards. "If you're a horror writer, that's going to happen," he says. "I've been shocked when I do get nominated. Anyway, I hate black-tie events." Darren's fans are certainly devoted; they call themselves 'Shansters', and his website gets more than 2,000 hits a day. His daily blog is also a huge draw.

He's highly disciplined about his work, sitting down at his desk at 9.30am and writing 10 pages a day -- about 3,000 words. On top of this, he may also write up to 1,000 words a day on his blog.

He's refreshingly candid about his writing. "I don't write books that I think will be popular; I don't write for a market -- I write books that I'm going to enjoy writing," he laughs. "Which is probably why some of them haven't been published. If I'm going to spend two years working on a book, it has to appeal to me.

"I've written about 20 books that haven't been published," he admits. "Probably never will be. Sometimes I go back and cannibalise them. I wrote my first book at 17; that's how I learnt." He's written everything from dark fantasies and science fiction to adult horror novels. One of his horror novels for adults, Procession of the Dead, has just been published under the pen name, DB Shan. "It even has romance in it," Bas reminds him with a grin.

Sometimes, he gets letters and emails from worried parents. "'We've got a son who wants to be a writer and some of his stuff is horrendous. Should I take him to a psychiatrist or something?' I always say, 'Don't worry, it's just a phase they're going through'. As a teen, you are more emotionally disturbed; it's a heightened state of being. It's easy as an adult to look back at that and laugh." But it's clear Darren has great empathy for teenagers, and that's one of the reasons his books have become so successful.

I must admit, driving to Darren's house, I wasn't at all sure what to expect. In general I'm not a horror fan, but after reading several of Darren's books I've realised they are more drama and suspense than horror, and his teenage characters are incredibly well drawn. And after hearing him talk so passionately about his craft and his fans, I have to declare myself a bona fide Shanster.Does Darren's amazing art and movie collection have something to do with it? Maybe. But it's all part of Darren Shan, the enigma.