Children's horror fiction is hard to avoid at the moment, but it is of varying literary merit, writes Arminta Wallace.

Ghoulies, ghosties and long-leggety beasties? Forget it. Today's kids are more likely to be reading about shape-shifters, shadows and streetwise vampires. Horror is the new Harry Potter.

The green slime department is becoming a permanent fixture of many bookshops as publishers scramble for a slice of an increasingly lucrative market; and with the age range targeted by horror fiction writers now stretching from six to adulthood and beyond, monsters are moving into areas where no monsters have gone before. "Reader Beware! You're in for a Scare!" is the tag-line on the cover of the Goosebumps series. Scoff if you like. The Goosebumps books clocked up average sales of half a million per volume internationally - which, when you think about it, is a pretty scary number of real live children.

The problem for parents is two-fold. Bring your children to the bookshop - or even the local library - and you'll find it difficult to avoid this type of literature. On the other hand, with electronic wizardry grabbing more and more of your children's time and energy, you may be happy if they read anything at all. Even Darren Shan?

"Yep," says Darren O'Shaughnessy, long-time resident of Limerick and creator of a top-selling 12-volume vampire saga. "Occasionally I get a critic saying 'Oh well, it's good that boys are reading - even if it's only Darren Shan'. But as people who are actually out there trying to get kids to read will tell you, kids are very demanding. If a kid doesn't like a book he'll put it down right away."

A regular visitor to schools and libraries all over the world - he's huge in Japan - O'Shaughnessy was bitten early by the vampire bug, and says he spent his teenage years up to his neck in "vampire movies, fantasy and adventure books. By my early 20s I'd got a bit bored with vampire books, because so many of them just repeated the same old Dracula story. I mean, Dracula was a brilliant book, but it's been done over and over and over. So I wanted to do something a bit different. But I still loved the idea of vampires."

Why would any sane person love the idea of vampires? He laughs. "Vampires are cool. There's no other way to put it. The fact they drink blood, that they come out at night; they're more believable than a lot of other monsters, you know? Zombies and so on?"

Drogheda-born Oisín McGann, author of The Gods And Their Machines and The Harvest Tide Project, also cites childhood reading as a major influence on his adult writing career. "The writers who made me want to write were the likes of Roald Dahl, and Tolkien, and CS Lewis - so I suppose when the imprint has been made, that's the one that's going to stick with you."

Parent, beware? "I've never seen any formal proof that if children read anything at all, they'll inevitably progress to reading something 'better'," says Robert Dunbar, a regular reviewer of children's books for The Irish Times. "On the other hand, I suspect there's a large body of people who read Point Horror and then go on to Stephen King, or whoever - and good luck to them. Adults who read literary fiction are very much in the minority of readers, in any case."

Even within the category of "horror" fiction, says Dunbar, there are books which have some literary merit and books which have none at all. On the whole, it's pretty easy to figure out which is which. Books which rely too obviously on formula, contain racist or sexist overtones, or are produced by a nameless corporation - as opposed to a real author - are ones to avoid, he suggests, while he would place Francine Pascal's Fearless series, whose heroine is a cross between Scully from The X Files and Buffy the Vampire Slayer, among those which cleverly subvert the expectations of the genre.

Ask someone who disapproves of horror books what they expect them to consist of, and they'll most probably say "gore and guts". Ask a child and they'll say something like "the guy pulls his face off and all the maggots fall out". The authors, however, tell a different story. "It sounds strange, given that I'm writing about vampires and circus freaks and so on," says Darren O'Shaughnessy, "but I think the books are moral books. They're about making the right decisions, trying to do good things, being loyal to your friends. I'm not interested in just grossing readers out."

The crucial component of "horror" fiction, it turns out, is that old chestnut - a rattling good yarn. Nobody knows how to spin one better than Anthony Horowitz, author of the BAFTA-winning TV series Foyle's War and the million-selling Alex Rider series of spy novels for children. Having written two volumes of scary stories, Horowitz is about to take a major plunge into horror with a five-part sequence called Raven's Gate.

"I don't think that gore and violence are necessarily important parts of horror - indeed, horror is more effective if you keep the blood count fairly low," he says. "I don't enjoy extreme violence. What I'm much more interested in is poking at the imagination; looking into the dark corners of the mind. There is a limit to how much I want to scare children. On the other hand, with this new series I want to push that limit as far as it will go."

This from the man who once wrote a story called Bath Night: "one mother told me that after she read it, her daughter refused ever to have a bath again."

Blood, then, isn't necessarily bad. In fact, the high-camp style of gothic horror is often more hilarious than horrible. "I find that black comedy aspect of it quite appealing, I must say," says Robert Dunbar. "I suppose any book that has a lot of corpses and death and decay gets to the point where it's sending itself up." Some of the titles - Graveyard School by Tom B Stone, or Spine-Tinglers by MT Coffin - are, ahem, a dead giveaway. "I would find it hard to believe," says Dunbar, "given the sophistication of today's children, that they're reading books like Goosebumps for much more than a laugh. Tomato ketchup on the corpse, sort of thing."

At the older end of the market, matters undoubtedly get more serious. Death is a recurring theme in many books for teenagers, as is the situation where a child is isolated, with adults either physically inaccessible or unable to see that there's a problem. This is usually - though not always - turned around when the child solves the problem, thereby taking control of the story.

In a similar way, the presence of monsters or supernatural beings allows horror fiction to play with such themes as fear of the unknown while using the safety net of metaphor. After all, vampires are not something we expect to meet at the supermarket. (Although, now that supermarkets stay open all night...)

There's nothing particularly new about any of this. One horrible plotline runs as follows. A pair of evil shoes condemn their youthful owner to a life of perpetual motion. She is promptly condemned to death for dancing on the Sabbath - only to be spared by a "kindly" executioner who cuts her feet off instead. As the reference to the Sabbath might suggest, that plotline has been around for quite a while. In fact, Hans Christian Andersen's sinister story, Red Shoes, was first published in 1835.

One thing is for certain: children's horror fiction isn't going to vanish in a puff of smoke any time soon. Oisín McGann has already written two books for the eight-plus age group, The Evil Hair-Do and The Poison Factory; his sequel to The Harvest Tide Project, The Fragile Stone, is scheduled for publication in the autumn.

Darren O'Shaughnessy has embarked on a series about demons, of which the first volume, Lord Loss, will appear in June. As for Anthony Horowitz, he is unrepentant about the fact that his new series pits five blameless children in a battle against evil.

"The idea is that evil and black magic and witches and devils and monsters exist inthe real world. That orcs, or whatever, walk the streets at night, just out of your sight. The truth is, we like being scared. There's no greater pleasure than to gather close around the fire in the dark and tell scary stories. And better to be scared by devils and demons than . . . well, today - for example - they're talking about America bombing Iran. Now that's much scarier than anything I can come up with."

The Saga of Darren Shan is published by HarperCollins, each volume £4.99 in UK. The Harvest Tide Project, by Oisín McGann, is published by O'Brien Press at €7.95. Raven's Gate, by Anthony Horowitz, is due from Walker Books in June.