One day the master spy novelist John le Carré was walking on Hampstead Heath in London with his son, the writer Nick Cornwell.

Le Carré, whose real name is David John Moore Cornwell, was afflicted with cancer, but a kind that you “die with rather than from,” according to his son’s recollections. Nick Cornwell (who writes under the penname Nick Harkaway) doesn’t remember the exact year, though it was sometime in the “metaphorical summer” of his father’s life. But he does recall with crystal clarity the promise he made: He would finish any incomplete work le Carré should leave behind after dying.

That pledge came to Harkaway’s mind in December when Le Carré died at the age of 89 after a fall at his home in Cornwall in southwestern England. He knew that there was, indeed, an unpublished work of his father’s called “Silverview.” The son looked it over and concluded it was not so much “incomplete” as “withheld,” he says in an afterword to “Silverview.”

A posthumously discovered work is one of the art world’s great intrigues, for it raises so many titillating questions, speculations, suspicions, hopes. Might this be the true expression of the creator’s soul? Might it be terrible?

Thankfully, what le Carré has left us, is a thoroughly enjoyable book, more accessible and less complex than his greatest works. This is not the sort of novel, like “Tinker Tailor Soldier Spy” or “Smiley’s People” that demands you stop mid-sentence, flip back 50 pages and start again from there. But “Silverview” still manages to build on themes Le Carré has developed so skillfully — betrayal, mendacity, bureaucratic inanity and our willingness to accept black-and-white explanations of a gray world — over decades as one of the world’s best-selling authors. Perhaps, his son wonders, le Carré held off publishing “Silverview” in his lifetime because it cut too “close to the bone,” portraying the British intelligence apparatus as unsure of whether it can justify itself and whether its mission is worth the cost.

It’s fitting that “Silverview” should arrive the same month as the latest James Bond 007 movie, “No Time to Die.” In Bond films audiences get a cartoon depiction of spycraft, with triumphs that are plain to see. A le Carré book, in contrast, is so rich — beyond the intricate, perfectly crafted story lines and brisk writing — because his spies, while enmeshed in or at least at the edge of grand moments of world affairs, are engaged in a more nuanced calling, with outcomes that may not even be clear to themselves. They are often beleaguered victims of office politics — one misstep away from being put out to pasture. They tend to be cuckolds, loners, misfits and other non-Bondian sorts — wary of each other almost as much as they are of the Crown’s enemies.

In “Silverview,” le Carré untangles the life of Edward Avon, a sly former intelligence field agent emotionally scarred from harrowing experiences during the Bosnian conflict. We first encounter Avon in a broad-brimmed Homburg and a dripping, fawn raincoat in a seaside British town in East Anglia where he is posing as a retired academic. Avon lives with his wife, a revered Middle Eastern analyst for the British intelligence services who is dying of cancer, in a fading mansion called Silverview that took its name as an homage to the philosopher Friedrich Nietzsche’s house, Silberblick.

Avon befriends Julian Lawndsley, a 33-year-old who has dropped out of his lucrative big-city financial trading career to open a small bookstore. Avon is an odd but irresistible sort, and it takes him no time to shimmy into the naive Lawndsley’s world by portraying himself as a school chum of the bookseller’s ne’er-do-well deceased father, a scandalized Anglican priest.

At one point, the younger Lawndsley is easily manipulated by Avon into delivering a secret message to a woman with whom Avon claims to be having an affair. “What does the well-dressed man wear for a blind date with his father’s friend’s mistress at the Everyman Cinema in Belsize Park?” he ponders.

Avon is being tracked by Stewart Proctor, the head of domestic security — “witchfinder-in-chief”— for the book’s fictionalized British intelligence service. Proctor is a man for whom “the very idea of a consuming passion” is bewildering, which makes Avon, a man prone to emotional attachment to people and causes, all the more elusive.

The people and places Proctor encounters in his inquiries about Avon are relics, stuck in bureaucratic bogs with little or no real relevancy. He speeds off to look into a breach at a nuclear silo called the “Hawk Sanctuary” that he imagines will soon be a tourist trap.

“It’s a blip, according to Head Office,” the man tells Proctor. “Last night, it was a lapse. Which is worse? Blip or lapse?”

Eventually, Proctor finds his way to the home of two retired spies — Joan and Philip — once the service’s “golden couple.”

Proctor’s cringeworthy, and frankly offensive, observations of them read like a metaphor for his increasingly jaundiced view of the service’s decline. He makes disparaging comments about Joan’s appearance and snootily makes note of her “elastic-topped slacks and . . . T-shirt with a wide-angle print of Old Vienna.”

As Proctor is preparing to leave, Philip pulls him aside. “The thing is old boy — between ourselves, don’t tell the trainees or you’ll lose your pension — we didn’t do much to alter the course of human history, did we?” Philip said. “As one old spy to another, I reckon I’d have been more use running a boys’ club.”

In an era when the failures and misdeeds of intelligence services around the world can shock and alarm, reading Philip’s remarks feels like a clarion call that slices straight to the bone, and hurts. John le Carré did not just leave the world an engaging novel, he also left us with a warning.

Manuel Roig Franzia is a Washington Post staff writer and former foreign correspondent.

SILVERVIEW

By John le Carré

Viking. 224 pp. $28