The great early works of John le Carré — and make no mistake,”great” definitely applies to his masterly fiction — abound in rich, poetic prose so thick and lush that if they were greenery you would need a team of machete-wielders to move forward.

Though he uses a lot of words, Mr. le Carré chooses only the precisely right ones, each as perfect and inevitable as the first wedding-night kiss. It is impossible to dispute that his pointillist dissections of Cold War spy networks are as real as works of fiction can be, which is to say more real than any work of purported non-fiction that covers the same complex ground.

When the Berlin Wall came down and America and the West defeated the Soviet Union and the East — which may not have entirely pleased the very Leftleaning Mr. le Carré — there was the problem of what, with the Cold War ended, a writer of espionage fiction was to do. It finished the career of Len Deighton, once bracketed with Mr. le Carré the way Hammett and Chandler remain the sure thing for those who write dust jacket blurbs for private eye novels (“in the tradition of Hammett and Chandler”) and as Christie and Sayers are forever linked as the two giants of cozy English detective stories.

Mr. le Carré has done a pretty good job of finding new theaters in which to place adversaries, though he has never again reached the heights of “The Spy Who Came in from the Cold,” “A Small Town in Germany,” “The Honorable Schoolboy,” and “Smiley’s People.”

In “The Mission Song”(Little, Brown, $26.99, 344 pages), the action, such as it is, mainly takes place on a remote island where a secret conference is being held. The ostensible purpose of the meeting is to bring peace and democracy to the much-beleaguered Congo, but the charmingly naïve hero soon learns that the goal is actually to precipitate a coup that will dramatically enrich several African warlords and some multinational companies.

Bruno Salvador, known as Salvo, is the son of an Irish father and a Congolese mother. His extraordinary gift for languages, especially minor African tongues, has given him a successful career as a translator in Britain, where he is much in demand by large companies wanting to do business in Africa as well as by the Secret Service. He has married a white upper-class English woman, much to the evident disgust of her parents, which seems to have pleased her.

Told in first-person by Salvo, the tone of “Mission Song” is light, a narrative of sardonic, understated drollery. His job as an interpreter is a parallel to the titular figure in Mr. le Carré’s “The Tailor of Panama,” also a bit fluffier than the work of the 1960s and ‘70s. Both characters are excellent spy material, slapped down in the middle of everything but invisible, so people who should know better speak freely in their presence.

Knowing that his marriage is going down for the third time as his celebrityjournalist wife repeatedly ventures to weekend conferences that no one else seems to go to, Salvo falls in love with a Congolese nurse, improbably named Hannah, whom he desperately wants to tell that he’ll be away for a few days. When he calls the hospital, the phone is answered by a fellow nurse, a woman so frustratingly slow that he says she moves “at African tempo. If something was worth doing, it was worth doing slowly.” Overhearing more and more bits of conversation in various languages, the light bulb finally comes on and Salvo conspires with his beautiful lover to try to prevent further devastation to a country that has already had enough to last awhile.

It has been Mr. le Carré’s practice in recent books no longer to portray struggles between powerful nations, but instead the efforts of individuals against powerful corporations and governments. And this is a good example of the no longer entirely fresh notion of pitting a couple of idealists against seemingly unstoppable forces.

Mr. le Carré evidently enjoys jocularity of tone as much as his protagonist does, having his characters describe a Chianti as “weapons-grade” and an old van as “walking wounded.” But in spite of the gentle humor and clarity of the prose, “The Mission Song” takes a long time to get going. Salvo’s job is to interpret at the top-secret conclave and the tale is told through his eyes and ears. Since he hasn’t a clue about what is going on, the reader is mainly treated to a couple of hundred pages of what amounts to minutes of a meeting, albeit one with more colorful participants than in the usual boardroom.

The author’s evident affection and sympathy for Africa is apparent, but hearing about plans for and key figures in Bukavu, Goma, Kavumu, Kivu, Kinshasa, Fizi, Baraka, Uvira, and Nzibira, all within a few pages, will probably make some eyes glaze over (or close).

Nonetheless, the charm of the innocent Salvo, eager to do some good for his country and for Congo, saves the day. How could anyone not like a guy who modestly says, “I’m not musical. My humming embarrasses me even when I’m alone,” and is mightily miffed when someone calls him a zebra?

Mr. Penzler is the proprietor of the Mysterious Bookshop in Manhattan and the series editor of the annual “Best American Mystery Stories.” He can be reached at ottopenzler@mysteriousbookshop.com.