Autumn now seems officially to be John le Carré season, given that this is the fourth year running since the author’s death in 2020 we’ve had a new book by or about him: first came the posthumously published novel Silverview, then an edition of his letters, as well as a memoir by his lover Sue “Suleika” Dawson (The Secret Heart), before last year’s follow-up exposé by his biographer Adam Sisman, The Secret Life of John le Carré, documenting other lovers the espionage writer hadn’t wanted mentioned in his lifetime.

Considering the drift of those books, it’s maybe unsurprising if we’ve lost sight of le Carré’s achievements as a novelist, especially in his early years. His first big hit, The Spy Who Came in from the Cold (1963), which mapped a thwarted romance on to geopolitical intrigue in divided Berlin, accelerated the spy genre’s 20th-century breakaway from jingoistic tub-thumping and gung-ho adventure. By the time of Tinker Tailor Soldier Spy (1974), an ensemble psychodrama in which the British plot against one another as much as against the Soviets, le Carré’s narrative energy is generated more by gnarly workplace tensions rather than conventional derring-do, which is nonetheless tinglingly present in the book’s shattering finale.

Karla’s Choice, perhaps the most intriguing of the le Carré-related publications to have appeared since his death, puts these achievements front and centre. Set after The Spy Who Came in from the Cold but before Tinker Tailor Soldier Spy, it’s a new mission for the spymaster George Smiley, from the pen of le Carré’s son, novelist Nick Harkaway, who makes clear that while this might have been a book he was born to write, it was far from easy. He describes sending the manuscript to the author Joe Hill, Stephen King’s son, “one of the few people on Earth who can claim to understand the scale of my fear around this book”, and the extent to which it’s a family affair supplies an off-page frisson that he doesn’t shy away from in a winning foreword. (Will the book succeed? “We’re about to find out.”)

Set in 1963, it centres on a vanished Hungarian émigré, Bánáti, a Soviet spy whose cover as a London literary agent has been blown after a failed attempt on his life by a Moscow assassin. When the incident rings alarm bells at the Circus – le Carré’s fictionalised MI6 – it drags Smiley out of retirement (not for the first time, as we know) in an effort to turn Bánáti into a British asset. The attempt – unsurprisingly unsmooth – involves a German double agent previously seen orchestrating a climactic double murder in The Spy Who Came in from the Cold, as well as – no spoiler this, given the title – Karla, the codenamed Russian infiltrator first seen in Tinker Tailor Soldier Spy.

In true le Carré style, though, Karla only appears here two-thirds of the way in; Harkaway faithfully reproduces his father’s rhythms at the level of sentence and plot alike, with slow-burn tension giving way to agonising jeopardy as cat-and-mouse games explode into crunching hand-to-hand combat or street gun battles. There’s a grippingly cinematic escape scene set in Budapest, as well as a lapel-grabbing speech about “the English mistake” (geopolitical ignorance, essentially). And of course there’s the jargon of the spy trade – “handwriting”, “babysitters”, “product” – and lessons in what it takes to succeed: someone mentions training in a dormitory with “a hundred different kinds of lavatory” (“nothing... more likely to blow your cover than an inability to contend with bathroom facilities you supposedly had been using from birth”). Dry comedy ripples throughout: one Soviet spy, asked his price for defecting, says he wants to star in a film with Peter Sellers.

There’s clearly an attempt to broaden the horizons of the original books – in any case, hardly so exclusively masculine as sometimes portrayed – but Harkaway misses no chance to bring the women of the Circus closer to the spotlight. Much of the action involves Bánáti’s employee, Susanna, another Hungarian, who is his assistant at the literary agency, left to pick up the pieces after his disappearance. As Smiley draws her into the plot to turn her former boss, she learns the ropes of spycraft – a neat way to avoid clunky exposition for the reader coming to le Carré’s world for the first time. Nor is Harkaway quite so reliant on delivering plot twists via Conradian nested monologues involving recollected interrogations or minutes and reports, a staple of the original Smiley novels. (Don’t fret, though, those are still here – expertly negotiated – to say nothing of le Carré’s occasionally reader-foxing tic of referring to the same character by both name and surname, seemingly at random.)

For fans, there’s much to enjoy. The collegiality witnessed here among the Circus crew – Toby Esterhase, Jim Prideaux, Bill Haydon and co – oozes pathos in view of the in-fighting and paranoia to come in Tinker Tailor Soldier Spy; ditto the agonising scene in which Smiley tries to make amends for missing a holiday with his wife by surprising her in Vienna, only to be told by the concierge at her hotel that she’s busy with her husband – a sign of further torment ahead. You needn’t be a le Carré nut to enjoy it, though, and while we’re undoubtedly in something of a glut of sequels and reboots, it’s far from unimaginative fan service. A loving tribute to a complicated father (as Harkaway’s dedication seems to acknowledge) as well as an excellent novel in its own right, and only the first of a new series, at least to judge from a broad hint dropped in the end matter. I can’t wait.

• Karla’s Choice: A John le Carré Novel by Nick Harkaway is published by Viking (£22). To support the Guardian and Observer order your copy at guardianbookshop.com. Delivery charges may apply