LONDON — The novelist John le Carré was recalling an encounter from a decade or so ago, as the cold war was receding into history, giving way to a new system of shadowy threats and uneasy alliances. Sir David Spedding, ill and retiring as head of the Secret Intelligence Service, or M.I. 6, had come to visit him at his house in Cornwall, and they were talking about the changed realities of spying. “He told me, ‘You can’t imagine how disgusting our world has become,’ ” Mr. le Carré said. “And I accept that. It is a disgusting world.”

At 76, Mr. le Carré is snowy-haired, droll and courtly, speaking in perfect paragraphs and exuding the air of quiet privilege and distinguished manner of a retired statesman. If he chose to, he could still be producing crowd-pleasing books about his most famous spy, George Smiley, late of M.I. 6, or easing into a gracious old age of playing with his grandchildren, lunching at his club and resting on his laurels.

But he is still sharp, still fizzing with ideas, and fueled by a new righteous fury. He has become, if not exactly radicalized, then at least clearer about his political views and more willing to articulate them. His latest book, “A Most Wanted Man” (Scribner), speaks to one of his preoccupations: the excesses, as Mr. le Carré sees it, of American foreign policy and the immoral nature of the intelligence practices that underpin it.

The message in the book, his 21st, is embedded, as always, in an absorbing tale: of spies and maybe-spies, of divided loyalties, of corrupted innocence. The title character is a young Muslim refugee named Issa, who suddenly and illegally surfaces in Hamburg and falls under the care of an idealistic young female lawyer. But then he becomes the object of a nasty and ill-conceived tug of war among feuding factions of several Western intelligence agencies, which cannot agree on whether he is a broken man or a dangerous terrorist, or perhaps a bit of both.