Horror writer Darren O'Shaughnessy is the grisly king of the playground. He talks to Sinclair McKay

Just occasionally, when one has wandered into a certain section of Waterstone's, one wonders what it must be like to be the sort of author who writes about hellish demons, throat-gouging werewolves, maggots emerging from corpses' nostrils and vampire bloodbaths. Darren O'Shaughnessy could tell you all about it.

Darren O'Shaughnessy writes for 'the unreachable reader'Better known to countless wide-eyed readers by the authorial abbreviation Darren Shan, he is described by his publisher, HarperCollins, as a "master of horror". A 12-volume sequence of vampire novels - starting with Cirque Du Freak and taking in Vampire Mountain and Tunnels of Blood - established his position, selling millions of copies, and his new 10-volume Demonata series is proving equally compulsive.

What makes O'Shaughnessy's stories truly distinctive, however, is that the gruesome and the macabre are being served up to a playground audience. If you have children, there is a very strong possibility that, at some point, their noses will be jammed in one of Shan's brain-squishing, maggot-swarming narratives.

"When the books were first published, I expected a backlash," says O'Shaughnessy disarmingly.

"I ran all the arguments for the defence through my head in case of hostile interviewers - ready to explain why the books aren't a disgrace, that they had a strong moral underpinning. But in fact, there wasn't any outrage. No one, save the occasional parent or teacher, was up in arms at all. In fact, teachers and librarians have very often championed my books."

But then O'Shaughnessy is aware that his young protaganists - the teenage "Grubbs" Grady and "Darren Shan" - are actually following in a grand literary tradition. As long as there has been gruesome sensationalist fiction, there have been young readers lapping it up.

For Jane Austen's generation, it was Ann Radcliffe's The Mysteries of Udolpho and Matthew Lewis's The Monk. Austen satirised the trappings of Gothic romance in Northanger Abbey. In the age of the Victorian periodical, teenage boys loved lurid Gothic serials such as Varney the Vampyre and The String of Pearls.

In America in the 1950s, there was a strident campaign against EC horror comics such as Tales from the Crypt and Vault of Horror, which some felt to be corrupting. And for those of us of a certain age, horror meant the early 1970s works of James Herbert (The Rats and The Fog) and Stephen King.

Those who have only ever seen the recent pallid remake of Salem's Lot don't know what they are missing.

O'Shaughnessy was brought up on a diet of Hammer horror, Shaun Hutson, and the film Theatre of Blood, in which Vincent Price murders Robert Morley by force-feeding him his two beloved poodles.

But O'Shaughnessy was also a fan of Roald Dahl and the Just William stories, and he studied children's fiction as part of his English degree. He has written adult novels, and has plans for more. But when an idea for a children's book - involving a youngster at a circus who is forced into becoming a vampire's assistant - occurred to him, he decided to give it a whirl.

By serendipity, he sent his manuscript to the agent Christopher Little, who at the time was also attending to the burgeoning career of an unheard-of author called J K Rowling. As with Rowling, it was the quality of the storytelling that quickly ensured that O'Shaughnessy's young audience grew.

His success has also been international. "Japan went mad from day one," says O'Shaughnessy, laughing. "The Shan novels sold unbelievably, topped the adult bestseller charts. I think they targeted 16-year-old girls. I travelled over there for publicity purposes. The reception was all a bit like Beatlemania."

These days, thanks to his fantastical tales of vampires and, most recently, the chess-playing demon Lord Loss and the different generations of mortals that have to fight him across the ages, O'Shaughnessy's domestic following is equally enthusiastic. For those who imagine that horror is strictly the province of bloodthirsty adolescent boys, think on and look sharp.

"Girls form about 50 per cent of the readership of my books," he says. "At signings, you sometimes see more girls than boys. From the start, it was very noticeable that girls were reading the novels. I went to HarperCollins, told them this, even suggested that perhaps the covers shouldn't be so horrific."

This suggestion proved over-sensitive. Indeed, these days, the horrific covers now glow in the dark (think how much more attractive the works of Margaret Drabble would be with such a device!) They clearly have not been off-putting.

Neither have the welters-of-gore set-pieces that characterise each book. Even for the grown-up reader, these tales are best approached some time after breakfast has been digested.

But as O'Shaughnessy points out, if they were merely blood and guts, then the books would not have held so many readers, girls or boys. They have to have heart as well, and running through the Demonata series is a strong sense of family, of the ties of love, although drawn with a marked lack of soppiness.

As has always been the case with a genre with special appeal to teenagers, the main subtext of the Demonata is puberty and growing up. Young "Grubbs" Grady may come from a family afflicted with lycanthropy, but it is also quite clear that outbreaks of fur and fangs have a metaphorical neatness.

"Yes, it's a coming-of-age story," says O'Shaughnessy. "But the point should be that good fantasy is more than just fantasy. Your body's changing, you're uncertain about the future, uncertain about your ability to face the challenges you have to face - and really, it transmutes into this fantasy about this kid who turns into a werewolf."

The writer, who is now 35, was born in London and retains the capital's distinctive vowels, despite having lived in Limerick for the last 29 years. When he writes - and his output, at two novels a year, is prodigious - he works in Ireland. When he is not writing, increasing amounts of his time are spent travelling around promoting his latest works.

Next month, he will be appearing at the Bath Festival of Children's Literature, alongside many other luminaries. His fans generally turn out in force for such occasions.

But while he is obviously tickled pink by his dual bestselling/cult status, he is also conscious that he bears an unusual responsibility to their readership. If young readers get pulled into his books - and getting boys in particular to read is no mean feat - then the hope is that their enjoyment of books will be cemented from that point.

"I write very short sentences, intentionally easy to read," O'Shaughnessy says. "I have no interest in writing something that only academics can read and understand. I always want to try to reach the unreachable reader, to put a book into a kid's hands, without using the phrase that I hate: 'Hey kids, reading is good for you.' I think that is the worst thing you can say to reluctant readers.

"The myth that kids don't want to read is put around by well-intentioned people, but the best teachers understand that you have to give children books that they have an interest in reading, and then the habit is picked up."

There is no doubt that the odd parent will feel a flutter of disquiet about their offspring reading about voracious demon dogs and supernatural beings with hollowed-out hearts filled with snakes. But O'Shaughnessy is blithe about kids' ability to cope with his brand of ghoulish excess.

"I have had hardly any feedback from fans saying they have had nightmares," he says, "I have had emails, however, saying that the books had made them cry. The emotion is there. So that is why I am fine with the horror-writer label."

 Darren O'Shaughnessy will be appearing at The Daily Telegraph Bath Festival of Children's Literature on Saturday, Sept 29