If a posthumously discovered novel is enough to set a conspiracy theorist’s antennae twitching, they’ll be wobbling like deely boppers when the novelist in question is the spymaster himself. But conspiracy theorists, while alert to the complex and absurd, are notoriously blind to the obvious. John le Carré was a working writer, producing a book every couple of years, and it would have been a surprise if he’d died leaving a clear desk. And it’s not as if he had reason to hang up his pen. While alive to the dangers of a novelist outstaying their welcome – he cited Graham Greene in that regard – his output remained consistently robust. If the late novels are slenderer and less layered than those he produced 30 or 40 years ago, they are also angrier and more politically engaged. He still had much to say. As for the complaint, occasionally heard, that in later life he wrote nothing as groundbreaking as The Spy Who Came in from the Cold, or as formidably comprehensive as the Karla trilogy, he might with some justification reply – à la Joseph Heller – “Who did?” The only important question, then, is: is Silverview any good? Thankfully, the answer is yes. A shaky start aside – the opening scene doesn’t really earn its place in the novel – the book settles down eight pages in, and for one last time we’re in le Carré’s familiar world: its themes, its principals, its impeccable style. Our hero is one Julian Lawndsley, a young man in flight from a City career, taking over a bookshop in an East Anglian seaside town despite having a blank canvas where a literary hinterland should be – he has never heard of Sebald or Chomsky. He has an early encounter with Edward Avon, a man “as mad as a flute”, who has plans for Julian and his bookshop basement, where he proposes they establish a “Republic of Literature”. Edward, the pivot on which Silverview swivels, is married to Deborah, a noted Arabist and one-time big wheel in the British intelligence service. She lies dying in the house for which the book is named. Edward’s own spook career, and the murky circumstances in which it ended, come to light as the service’s head of domestic security, Stewart Proctor – “Proctor the Doctor” – starts to pick away at his past while investigating a leak of classified information. There are wobbles and coincidences here, certainly. It remains a happy chance that Edward was at school with Julian’s father, whose own sketchy biography – he was a fire-breathing born-again Christian preacher, until the moment he lost his faith and became a public disgrace – seems included more to satisfy le Carré’s own longstanding fascination with difficult fathers than because it lends anything to the plot. And the love affair that blooms between Julian and the Avons’ daughter Lily might as well be preordained; she reaches for his hand as soon as she meets him, without any of that drawn-out getting-to-know-you nonsense. As for Julian himself, it’s a strange 33-year-old who abandons what was evidently a high-flying City life (“I was a wide-awake predator from day one”) and opts to be absorbed into the lives and secrets of odd new neighbours. Like one or two of le Carré’s other young male protagonists, Julian has both more than and not enough of a past to entirely convince. But against this, Silverview has three outstanding set pieces, any one of which more than outweighs weaknesses of plot. Proctor’s interrogation of two retired colleagues, in which Edward Avon’s history is anatomised, is le Carré at his finest, revealing character and backstory through dialogue with an economy and grace beyond most writers. The service funeral is pure social comedy (“Do you realise? The whole of F7 has turned out! … Isn’t that absolutely marvellous?”), reminding us that no one was better at showing that spies are just like everyone else. And then there’s Proctor’s visit to a classified outpost, an airstrip with a subterranean facility attached: a “dedicated nuclear hellhole 300 feet below ground”. This is closer to standard thriller territory than le Carré usually came, but where other genre writers might pump up their volumes with prolonged action sequences, here the conversational duelling is as exciting as a car chase. Roadside attractions include glimpses of the lost children and junked marriages of service life, alongside moments of pure le Carré, such as the indignant administrator’s refusal to believe that Proctor is investigating a “technical” breach: “I mean a breach is people. It’s not fucking fibre optics. It’s not tunnels. It’s chaps, surely?” Because chaps, surely, are le Carré’s subject, here as always; chaps and the loyalties they inspire, the causes they embrace, the institutions they betray. Women, on the whole, come to life in his pages only when age, illness or eccentricity removes them from his chaps’ arena of sexual interest – in Silverview, this applies to Deborah Avon and Celia of Celia’s Bygones, the shop adjoining Julian’s, who chain-smokes cigarillos in her parrot-green and orange kimono. Lily Avon – despite effort on her author’s part – never catches fire. Perhaps the real purpose of that preliminary scene, featuring Lily and Proctor, is to provide her with a function above and beyond that of Julian’s love interest, but if so it’s too little, too soon. Meanwhile, the chaps chase their destinies. Like George Smiley before him, Proctor is haunted by suspicions of marital infidelity even while uncovering grander treacheries – if treachery is even the word. In the intelligence community, we learn, anything short of pragmatism can be a grave security risk. While le Carré’s villains betray their countries for ideology or – worse – money, his decent people do so for love and idealism, a theme running through pretty much every novel he wrote. They replace a worn-out loyalty with a consuming passion, which demands their absolute commitment; in Silverview the grail lies in Bosnia, where the world’s sins are written large. Besides, Proctor comes to wonder, what precisely is being revealed here: the service’s plans or its paralysis? Or is the service itself the problem, getting “in the absence of any coherent foreign policy … too big for its boots”? With such asides, it’s small wonder some of le Carré’s more savage critics came from within the intelligence community, and yet he remained to the end deeply involved in that world. In this novel he still has tradecraft to impart (when sensitive matters are under discussion, choose a bare room with no party walls and no chandelier) and human touches to reveal, such as the photo glimpsed on a study wall, showing the service cricket team. Behind it all there’s the familiar lament, more melancholy than cynical, from those who have dedicated their lives to ideals that have been betrayed by one government after another. “We didn’t do much to alter the course of human history, did we?” one former spook observes. “As one old spy to another, I reckon I’d have been more use running a boys’ club.” “Silverview”, we’re told, is a reference to one of Edward’s hobbyhorses, Nietzsche, who lived in a house called Silberblick. But it’s hard not to see it as the author’s nod to Ian Fleming, whose own house was famously called Goldeneye, and who some critics thought had been rendered obsolete by le Carré. (Readers, a more easygoing bunch, would probably agree there’s room for both.) It would be an appropriate tip of the hat. Because whatever claims towards literature might be made for him – claims easily justified by the best of his work – le Carré’s greatness has its roots in his mastery of spy fiction; a genre he augmented with novels notable for their craftsmanship and humanity, and writing for its stealth and sophistication. With the publication of Silverview, it’s clear these virtues remained intact to the end. And if this final novel contains the occasional passage where we might feel we’ve been here before, such moments are tempered by the sadness of knowing we’ll never be here again. Mick Herron’s latest novel is Slough House (John Murray). Silverview by John le Carré is published by Viking (£2o). To support the Guardian and the Observer, order your copy at guardianbookshop.com. Delivery charges may apply.