“I WRITE instinctively, responding to impulses,” says Christopher Priest. “Most of my books since The Affirmation have a double quality — on one level, the main one, they are stories to be told, intended to be enjoyed, and which will probably contain some ideas that intrigue the reader.

“The second level is a sort of invitation to the reader to join in the process, to see and understand the book from another viewpoint, to accept that it is fiction.”

Written in 1981, The Affirmation is set in a region of wonders called the Dream Archipelago. It was my portal into Priest’s witty and philosophical science fiction, which tackles deception, the plasticity of reality and the malleable nature of memory and perception. Subverting genre conventions, it explores the nature of storytelling.

“I often say that the act of reading is as creative as the act of writing — everyone has a unique imaginative response to a book — and this is part of what I’m getting at. You can read my stuff on the main level alone and it will be enough but if you open your mind to the other, then I think and hope there’s an extra level of enjoyment to be found.”

His 19th novel, The Evidence, is a gripping and erudite blend of sf, literary inquiry, murder mystery and Kafkaesque paranoia. Priest is back in the Dream Archipelago, where events are ambiguous and knowledge provisional. Its thousands of islands offer endless possibilities in terms of climate, culture and politics. What else draws Priest back to this protean landscape?

“Sometimes a story seems right for the Archipelago, sometimes not. The appeal of it to me is that it’s an open architecture that explains itself. There are several things it is not. It’s not just a background, not a ‘world’ in the current cliche in fantasy circles.

“It’s not a series — all the novels stand alone. It’s not consistent from one book to the next. It is all about geographical place and position but it defies being mapped.

“Often the weird nature of the place is part of the story: two islands with similar names on opposite sides of the globe, the map references identical but a mirror image of each other. The impossibility of mapping a place where the islands seem to change shape all the time or where crossing a narrow strait from one island to another propels you forward or back in time and so on.

“It’s not whimsy because the place is realistic. People live and work there and have to deal with these things and they also have familiar stresses and problems. But the climate is good, there are terrific surfing beaches, endless opportunities for hedonism, a general anti-war attitude, benign governments. Also, big hairy insects which chase you and kill you by planting their fertilised eggs in you. But I’m still dead serious.”

In The Evidence, crime writer Todd Fremde visits Dearth, a frozen and heavily industrialised island, for an academic conference. Dearth is an authoritarian society, claiming to be crime-free but retaining an armed police force and the institution hosting the conference is contemptuous and hostile and Todd encounters spatial and temporal upheavals known as “mutability.”

Motivated by his ability to craft a compelling crime narrative, semi-retired cop Frejah Harsent tells Todd about a murder that has remained unsolved for 15 years. As one subjective narrative is swept away by another, Todd becomes embroiled in a perplexing and potentially dangerous quest for the “authentic” version of events.

In several chapters Priest sets out the difficulties and limitations of detective and police procedural novels before tackling them within the narrative. Did this process emerge organically, as the story unfolded, or was it embedded in the story from the outset?

“With The Evidence I imagined the general scenario first, then set about finding how it would work by actually writing it. This to me is the real reward of writing a novel — a private revelation, the discovery of connections, the magic of metaphor, the power of narrative.

“I felt the book would have to include a locked-room mystery but the whole notion has been so often worked and reworked by thriller writers that it seemed a ‘ludic’ thing to do. But as the story developed and I knew more about the characters, it became irresistible.”

Priest’s assessment of the constraints of the detective story includes a reworking of the Agatha Christie “drawing room denouement,” reminiscent of Penn & Teller’s ability to reveal the mechanics of their stage magic without compromising an audience’s sense of wonder.

The story’s resilience to literary game-playing is a testament to the intelligence, power and elegance of Priest’s writing. Is he consciously challenging the tropes and traditions of genre and literary fiction?

“Challenging the tropes? No, I work with them. Every novel I’ve published has been fantastic in nature. I believe in the fantastic as a crucial part of literature, misunderstood by many, reviled by some, endlessly unfashionable in the literary world, but a source of fascination and inspiration to intelligent readers.

“Challenging the traditions? Now you’re talking. I’ve already said what I think of detective novels and their traditions. The sf world is obsessed with precedents and traditions, to its disadvantage. I distance myself from much of the current conversation within the genre about perceived trends and observances.

“I don’t know what the traditions of literary fiction are but anyway I don’t see literary fiction as an ideal.”

In several books — A Dream of Wessex, The Prestige and now The Evidence — Priest reflects on the demands of creativity during which characters suffer crises of the imagination but persevere. I ask to what extent he believes creativity is central to making sense of the world and surviving its challenges.

It’s a question that obviously touches a nerve: “In this world of demagogues, a referendum result from a minority of the population that is going to bankrupt this country, a Brazilian dictator who sees it as his mission to destroy the Amazonian wilderness as if it were his own, clerics who urge their followers to defend their religious beliefs by killing themselves and as many innocent people as possible.

“[There’s] a resurgence throughout Europe of neonazis, a climate disaster taking us all to hell and, until very recently, a moron in the White House and a supine British government dominated by a high-threshold unelected ‘adviser’... in this world, the one remaining hope for sanity is for creative artists and writers to stay calm but alert, to keep imagining the strange, inspiring, disconcerting and wonderful images that none of these populist aggressors can anticipate, understand or control.

“Artistic expression brings hope and independence.”

The Evidence is published by Gollancz, £20.