This novel is highly deceptive. On the surface, it is about the impact of the 9/11 attacks on those it left behind. It then goes into some of the less lurid conspiracy theories; Priest makes the case for the evidence presented so far being seriously lacking. In this, you might think we were in similar territory to Ken Macleod's Intrusion, where another science fiction writer goes a bit off piste to orthodox political thinking for the purposes of building a contrarian viewpoint to provoke debate. But that isn't Priest's intention at all.

Priest introduces us to Ben Matson, a British journalist whose girlfriend goes missing on 9/11. He believes her to have been a passenger on American Airlines flight 77, which crashed into the Pentagon. but her name appears on no passenger lists. As he investigates her fate, he becomes increasingly sceptical about the official narrative - and then a crashed jetliner is found off the US coast which seems to have come from nowhere - no corresponding aircraft has been listed as missing, and the US Coastguard suddenly declare that the wreck is not a jetliner after all, but rather a ship sunk in World War 2.

As the story develops (told in numerous flashbacks), we meet Kyril Tatarov, a mathematician born in the Soviet Union but now an American citizen. Possessed of a brilliant mind, Tatarov has evolved a theory that extends from the mathematical into the social, proposing that in a world governed by social media, with more and more people being exposed to a range of opinions about what others think happened, that consensus can reach a point where reality warps and what people think happened becomes the new reality.

In a world where political debate is now governed, not by facts but by "optics", this idea seems all too possible, though the only reality being warped in our world is that inside our own heads - for the moment. Yet we have long understood that "history is written by the victors", and "a lie can be half-way round the world before the truth has got its boots on", and similar ideas are part of the currency of modern political and social debate. How long before actual facts are bent to suit the consensus - and how long before we cease to notice it?

But beyond this, Priest is playing games with us. On one level, the title allows for some ambiguity from the outset. Is An American Story a story from America, or is it a story about an airliner, in the sense of Hitchcock's North by Northwest? Or both?

And there are other clues that point in a different direction. Priest's three books immediately preceding this one - The Islanders, The Adjacent and The Gradual were all, partly or mainly, set in Priest's fantastical seascape of the "Dream Archipelago", on a world very much like ours but home to a large number of islands scattered across a world-ocean which are subject to strange time dislocations, making the business of travelling from island to island more complex than just dealing with different administrations and their varying rules for entry, exit and customs. This book is firmly set in our world, but part of the action takes place on the Scottish island of Bute, or Eilean Bhòid in Gaelic - just as the islands in the Dream Archipelago have their common name and their local, patois name. Priest describes the seas around Bute, and the ferries that ply these seas, in the same way that he described the islands of the Dream Archipelago in his previous books. And the arcane and sometimes seemingly pointless bureaucratic processes that travellers in the Dream Archipelago encounter when arriving on a new island seem echoed when Matson arranges to interview Professor Tatarov in a mysterious American intelligence establishment suddenly set up in a disused hydropathic resort on Bute (which vanishes almost without trace a few years later).

Just to increase our sense of dislocation, the book was written in 2017-18 but is partially set in around 2021; Priest's idea of the fate of post-Brexit Britain, with a pro-EU Scotland declaring independence adds to the feelings of dislocation; a Balkanised Britain is a theme that Priest has hinted at throughout his writing career, and it certainly adds to the reader's unease. There is an element of autobiography in all this, as later in life Priest settled on Bute and lived there until his death earlier this year.

All in all, then, this was a book that made me think. At the end of the novel, Ben Matson finds some evidence he can believe in, no matter where that leads him. How the evidence got there is never explained, but within the context of the story it all makes some sense - but that leads to other parts of the 9/11 narrative being undermined. Perhaps this all takes place in a world where reality really is malleable - there is an Easter egg in the text that gives readers of other Priest novels a hint - but ultimately this is a novel designed to challenge our own complacency about the world we are making for ourselves. ( )