There’s a blurb on my copy of Gnomon where Warren Ellis explains how much he hates Nick Harkaway for having written it. I can relate: the ambition of this book would be enviable even if the execution weren’t very impressive. And the execution is very impressive indeed.

I need to capture Gnomon’s essence in not many more words than it has pages: a daunting challenge in its own right, made harder by my heaping praise on it in my opening paragraph. Readers familiar with my reviews will know I hold no truck with the Spoiler Police, but I’m nonetheless hesitant to reveal too much—not because outlining the plot would spoil your enjoyment of it, but because it’s effectively immune to summary. There’s just too much going on.

But still, let’s give it a go. For the setting, we have a dystopian future UK of the algorithmic-panopticon type: cameras and sensors everywhere, AI running all the things, democracy driven by mandatory online plebiscites covering everything from local disputes to major reforms of the legal apparatus. (It’s like the blockchain-enabled Society Of Tomorrow™ that features in TED talks, which is of course the point.) There are no police any more, only the Witness, one of whom – Meilikki Neith – is our viewpoint character.

Neith has to investigate a high-profile case: the death in custody of a suspected dissident. Dissidents like Diana Hunter are routinely identified by the System and brought in for questioning; more often than not, their dissidence is diagnosed as some incipient or as-yet-unnoticed mental illness or social dysfunction, and is treated before they’re released to go on with their lives in a happier, more well-adjusted manner. The treatment and diagnosis are performed by the same means: a combination of innovations that make it possible to read human mindstates with an astonishing level of fidelity, and also to edit them. It is during such a questioning that Diana Hunter, minor novelist and luddite recluse, died. The rarity of such deaths merits Neith’s investigation—she’s one of the best—because it’s important that the System be seen to be fair, that due process is followed.

The procedure is for Neith to review the memories retrieved from Hunter’s mind, so as to check whether she was the dissident that the System considered she might be, and whether her death was thus akin to the suicide of a captured enemy agent—to see if she had something to hide, in other words. Hunter’s memories are duly dumped into Neith’s mind. But while she’s waiting for them to settle, she decides to go gumshoe around in Hunter’s anachronistic house. The place is a Faraday cage, lined with books, devoid of cameras and sensors, and thus effectively off-grid in panopticonic terms. There, Neith meets an oddly-named androgyne who asks her a series of confusing questions, before roughing her up and doing a runner. In the aftermath of this assault, Hunter’s memories begin to surface in Neith’s consciousness… only it seems that they’re not Hunter’s memories at all, but those of a succession of other characters.

These could almost be treated as novellas in their own right: first-person accounts which bring the experiences of their narrators into sharp and immediate (if deliberately foreshortened) focus. Kyriakos the stock-market whizz-kid gains a god-like ability to see where the markets will turn, only to see them—and the rest of the world—turn sharply downwards. The alchemist Athenais is assigned to solve a Byzantine murder mystery that occurred in an occult contraption of her own fraudulent invention, and ends up on an inter-planar vision-quest. Berihun, a feted artist in the last years of Haile Selassie’s Ethiopia, finds his creativity revitalised when invited by his games-designer daughter to contribute to her latest project, a dystopian surveillance-society RPG that presses all the wrong political buttons in a very Brexity contemporary Britain. And in a post-human far future, the book’s eponymous character takes up a tainted offer that might let them bring an end to all things, now, then, and forever more. As we move through these accounts, interspersed with Neith’s attempts to make sense of the mind they tumbled from, we realise that they are not mere nonsense that Hunter had hidden in her head, but something larger and stranger and more interconnected than that.

The central notion isn’t exactly original—it’s rather Strossean, in fact. I doubt I was the only reader who, a third of the way through, had a solid notion of Harkaway’s intended trajectory, not to mention an inkling of why he was going there. Perhaps this is a thing that only a writer would say, but there’s a sense in which the real protagonist of Gnomon was Harkaway himself: much tension came from wondering how, if ever, Harkaway was going to land this thing without tearing off the undercarriage and ploughing into a passenger terminal. I was prepared for (and would have forgiven) a moderately bumpy or abrupt landing, an ending that tried to play the game straight while using a doubled deck of cards. Heck, I’d have probably forgiven a hammer-it-home boot-on-a-face-forever conclusion—though that’s almost the exact opposite of what you get, even if things are far from happily-ever-after.

But I never imagined Harkaway would have the audacity to have the book itself address me so directly and plainly in its final pages, to state its metafictional purpose while simultaneously claiming its own success… and yet he did, and it does, and it works (at least for me, shameless postmodernist that I am).

There’s so much more I could say, so much more I want to say, so much more I don’t know how to say. So I’ll just say: you should read it, it’s a masterpiece.