In his acknowledgements, Andrew Caldecott speaks of the challenges in placing this novel, a debut which, to his mind, resists easy categorisation. Yet while Rotherweird has singular qualities, it also undeniably belongs to a tradition: a particularly English weave of fantastical fiction. It's impossible to read it without sensing the shades of the greats: Lewis Carroll, Mervyn Peake, Neil Gaiman or Susanna Clarke – and that's just for starters.

Taking up this formidable baton with brio, Caldecott’s fictional world, like the metamorphs “creatured” by his dark necromancer, Geryon Wynter, is a gloriously unsettling composite. Familiar things mash-up into a strange newness. You don’t need Sasha Laika’s gorgeously naive illustrations to visualise the eponymous river island town, with its drawbridge and portcullis, tottering high-rise oak-and-plaster towers. A steampunk Tudormodernist folly; Portmeirion on acid.

Its transport modes are equally idiosyncratic: charabancs and vaulting poles, coracles and the odd bicycle. When apparent “outsider” Sir Veronal Slickstone defies these conventions, gliding through the gates of the long-deserted manor in his black Rolls Royce, ripples both material and spiritual shudder through the town’s carefully-preserved, carefully-erased collective psyche – and a story is born. Though “excavated” is perhaps a better word. Because Rotherweird’s most dangerous secret is its own origins.

Through a shifting, flitting, multiple point of view, Caldecott takes us on a compelling cat’s-cradle identity quest. En route we are drawn into a seemingly Manichean struggle between good and evil. There are villains, heroes and high stakes – the annihilation of not one, but two, frail, beautiful worlds. But appearances can be deceptive; deft and agile as its protean antagonist, this novel ultimately slips between polarised moralities to investigate something far more complex.

Mysterious compartments

Nestedness is woven into the book’s fabric in an almost Escherian way, evoking Tudor astrolabes, or diagrams of atomic structures. Secrets reveal secrets reveal secrets. Rotherweird, a hidden world, is full of buildings themselves hiding false ceilings and mysterious compartments. Crucially, it is a gateway to an even more hidden domain – Lost Acre – accessed by lodestones and populated by chimeric monstrosities. In turn, Lost Acre guards its own secret nucleus, a patch of “slippery sky” – a quantum, alchemical wormhole which wreaks havoc or miracles, depending on who’s using it.

Each character has their own slippery patch too; a soft spot leaving them vulnerable to manipulation. This key – their psyche’s core truth – is itself hidden, like DNA, in the letters of their anagrammatic names.

In its fantastical logic, Rotherweird is always coherent, but how it speaks to the non-fantastical is often sublime. It understands history and the perils of historical amnesia. While arguing for science, it delicately distils the ethical quandaries of tinkering with Nature, summoning the spectres of agribusiness, GM foods, deforestation and species extinction with allusive, devastating simplicity: "They do many things to living things."

Above all, the novel is a lodestone to its own Lost Acre: Englishness. Echoes of Shakespeare's John of Gaunt and Tolkien's Shire, both written during conflict, ring through gardener Hayman Salt's lovely paeon to a bluebell wood: "This was old, forgotten England". But which England is Salt talking about? The hub of innovation and artistry that birthed "the educated Elizabethan mind" which so delights Rotherweird's beguiling ninja-physicist, Vixen Valourhand? Or a post-Brexit isolation chamber, perched on the edge of a new doom?

Perils of whimsy

While there is plenty to savour in this engrossing debut, some of Caldecott’s storytelling choices come at a cost. Occasionally, whimsy threatens to overwhelm – we’re told punning is one character’s forte, but actually it’s an occupational hazard for all Rotherweirders. Similarly, when we might expect anagram fiend Marmon Finch to solve a central mystery, it’s another character who does.

This lends a certain haziness to the cast, despite the vivid descriptions; a quality reinforced by Caldecott’s restless, mayfly viewpoint. Frequently – though never in the spare, subtler “old history” sections, which gracefully unravel the town’s necromantic origins - I found myself yearning for more inner time with its inhabitants, particularly those caught in the story’s gnarlier moral nodes.

Perhaps that’ll happen. Rotherweird is only the start of a trilogy. Call me greedy, but I’m already itching to return to Caldecott’s universe – those crazy towers, those flawed nubs of humans, and, most of all, those entrancingly poignant, beautiful-ugly metamorphs.

Mia Gallagher is writer-in-residence at Farmleigh. Her second novel, Beautiful Pictures of the Lost Homeland (New Island, 2016), was The Irish Times book club choice in February 2017