It has been 20 years since Channel 4 aired Darkplace, but its cult appeal remains so intense that even today Garth Marenghi’s fans ask detailed questions about very specific plot points. It gives the Q&A segment of his TerrorTome book tour the air of a horror convention, with devotees in thrall to every last detail of canon.

This is, surprisingly, the first Marenghi book published in our realm. In the fictional world he usually inhabits, he’s written hundreds of preposterous potboilers, such as Afterbirth, in which a mutated placenta attacks Bristol, and Black Fang, in which rats learn to drive a bus.

In TerrorTome, we meet the alter ego’s alter ego, Nick Steen (and, in later chapters, even the alter ego’s alter ego’s alter ego, but no time to explain that here). Steen buys a cursed typewriter from a mysterious shop selling ‘uniquities’ – and eels – that taps into the darkest recesses of his imagination. Several freaky sex scenes later, he’s face-to-flayed-skull with the monstrous Type-Face, Dark Lord Of The Prolix, who brings all Steen’s horrors to life to terrorise the town of Stalkford.

The book is a delight, whether you’re a devotee of the shlocky 1980s horror genre or not. TerrorTome is a pitch-perfect parody of terrible genre writing, with overblown, clichéd prose and heavily signposted metaphor. All of Steen’s nightmares stem from the most unthinkable horror of the lot: that his work might get pulped. Meanwhile, his worldly nemesis is his editor Roz, whose only motivation is to ruin his works of genius.

Marenghi is a brilliantly aloof and self-important creation with an underlying inferiority complex, the Alan Partridge of horror writing. Even in print, he desperately defends himself against the criticism he knows he’ll get for clunky plotting or an inability to write female characters without ever actually addressing the problems.

The man behind the dream-weaver, Matthew Holness, has a keen sense of absurdity, and a gift for picking just the wrong word or phrase. He writes paragraphs of blunt exposition, often in entirely unrealistic direct speech. It’s a real talent to write this badly, this well.

Despite the preposterous plotlines, from Steen ending up liquidised in a mug (he recovers) to a lunatic making a ‘bone bride’, the richness of the prose is hilarious. The humourless pretension of his alter-ego is at odds with the absurdity of his work in which no metaphor is ever ambiguous and no subtext knowingly deployed.

Reading it, you hear Marenghi’s portentous, pretentious voice in every paragraph, but to have him read it on stage is a real treat, with every inflexion finding new ways to say things uniquely badly. A cassette recorder provides a (self-composed) backing track with the same absence of slickness.

Marenghi modestly presents the live show as a masterclass in how to write the perfect horror book, with each extract an exemplar of building tension, advancing action or titillating with erotic promise. If we laugh at his words – which we very often do – it is merely the safety valve of our unconscious releasing the intense fear his prose has instilled.

The second half is the Q&A session, which he sets up hilariously as an interview with himself, though he reluctantly realises the limitations of that format and opens it up to hoi polloi in the audience.

Holness inhabits his alter-ego so completely, never once casting doubt on Margenghi’s belief that he’s a serious, heavyweight author, that he’s able to improvise answers to whatever the audience throw at him. That Marenghi is so aloof and self-important that he can shut down some of the more esoteric or bizarre inquiries with a taciturn ‘no’ helps – though it’s a device he uses a bit too liberally.

Because it’s dependent on audience input, this (overlong) section is inevitably a bit scrappy, especially after the comedy gold of the book reading. Though even here, Holness sometimes improvises the perfect answer. His suggestion for the woman who thought her cat possessed was brilliant: ‘Drop a sofa on it,’ he recommended. ‘If it stops mid-air, the cat is under a spell of protection.’

• An Evening of TerrorTome With Garth Marenghi tour dates. Garth Marenghi's TerrorTome is also available from Amazon, priced £12.59.

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