George Smiley saves the day -- yet again; Smiley's People, by John le Carre. New York: Alfred A. Knopf. $10.95.

Smiley of "Smiley's People" is George Smiley, the owlish cuckold who delights in polishing his Mason-jar lens spectacles with "the fat end of his tie." A totally inadequate man and totally smashing intelligence operator, Smiley has appeared in seven of John le Carre's nine books -- and in the last three as ringmaster of the Circus. To new le Carre readers the Circus refers to British Secret Service headquarters in London, near Cambridge Circus.

Smiley (and perhaps le Carre himself) has always been of divided mind about the morality of spying. Indeed, it is the moral posture of the novels which, in part, sets them off in their own special niche of the genre.

"Why isn't Smiley here?" asks Alec Leamas of Control in "The Spy Who Came In from the Cold" (1963), le Carre's best-known thriller. Because, Control responds, "He doesn't like the operation. . . . He finds it distasteful. He sees the necessity but he wants no part of it."

Toward the end of "The Honourable Schoolboy" (1977), Smiley writes: "I have learned to enterpret the whole of my life in terms of conspiracy. That is the sword I have lived by, and as I look round me now I see it is the sword I shall die by as well."

Smiley's soliloquies in "Smiley's People" are extensions of this philosophy. Stalking Karla, Moscow Center's big bad bear who spoiled Smiley's work by planting the infamous Bill Haydon (read Kim Philby here) in the Circus and who "tainted" Smiley's beautiful and faithless wife, Ann, the compassionate spy master cries: "How can I win?. . . . alone, restrained by doubt and a sense of decency?"

But even as he lays the trap for Karla, the man who had escaped his grasp in Delhi years before, there is something in Smiley that hopes the trap will snap shut, empty.

In "Smiley's People," Mr. le Carre performs as the master magician of the thriller at the top of his form. From the discovery of a former Red Army general shot dead on Hamstead Health to the striking denouement to a Berlin reminiscent of the cold war, Smiley and his people are superb entertainers. London, Paris, Hamburg, Bern, and Berlin are the principle settings.

If one day the philologist in George Smiley prevails over the intelligence agent, and he stops chasing smuggled Circus files, high above Sussex Gardens in the Hotel Islay, John le Carre had better look out -- for the thriller aficionados of the world will run him to ground, no matter what cover name he's hiding behind in Penzance, Hampstead, or Switzerland.