THE QUESTION HAS been raised several times in recent years: how often can John le Carre drag poor, tired, disillusioned old George Smiley out of retirement and run him off on another adventure? Smiley's People seems to give a definitive answer: this one last time and then no more.

What's motivated Smiley in the past has been his loyalty to old comrades who get into new trouble; his intense, mixed feelings about his beautiful, faithless wife Ann; his long-standing, personal and idealistic vendetta against Soviet master-spy Karla. Above all, perhaps, he has acted because of his dedication to the continued well-being of the Circus -- that curious, bumbling, smart but careless British intelligence agency that time after time he has had to pull out of hot water.At the end of Smiley's People , nothing is the same, nor will it ever be again.

But what really points to this volume as the end of George Smiley is the sad deterioration of the Circus. In Smiley's heyday, the Circus was a group of brilliant amateurs, playing at espionage in old-school style as though it were a particularly complicated form of rugby. Now they have become (at least at the top) not professional (which implies a certain level of competence) but careerist -- which implies political orientation, a hunger for personal security, great attachment to the pecking order and procedural minutiae, and an unwillingness to face uncomfortable facts.

"The Circus has joined the Boy Scouts," says old comrade Toby Esterhase in one critical conversation, and that doesn't say it all, but it says enough. There is nothing left in the Circus worth Smiley's effort to save or anyone else's effort to eliminate.

With the institution hollowed away to insignifiance, Smiley's People is, as its name implies, a personal sort of book. Smiley dusts off and straps on his slightly tarnished armor one more time, not for the sake of the Circus but because an old comrade has been murdered, and the Circus simply wants to sweep the event under the carpet. His interest picks up when he glimpses a chance to settle his personal score with Karla, and in working out his scheme he uses not the current institutional resources of the Circus but an old-boy network of operatives who used to work with him.

The emphasis on the personal is even more remarkable on the other side of the curtain. Karla, who has acted in previous books as a sort of espionage machine, is suddenly vulnerable, and the vulnerability is rooted where it always is, in love. Being Karla, the superfoe is willing to lie, manipulate situations ruthlessly and kill innocent people without a second thought, all in the name of love. Yet Karla's feeling is nonetheless genuine, and when Smiley decides to adopt his enemy's kind of tactics, the game is over. To the extent that Smiley has become that which he used to fight, he has lost.

The espionage novel has become a characteristic expression of our time, as tragic drama was in Periclean Athens or the love sonnet in quattrocento Italy, and John le Carre is one of the handful of writers who have made it so. The fact that this form of writing has assumed this importance tells us something essential about ourselves, as does the content of the best books in this form.

Smiley's People is such a book, and what it tells us is clear enough: that we are now engaged in an intense dialectical process; that the terms on which the process operates have no regard for traditional human values except as points of leverage, and that the goal toward which the process tends is synthesis. We move, inevitably, toward a merger with that which we oppose: Karla begins to resemble Smiley and that resemblance is his downfall, because Smiley has begun to resemble Karla -- which is Smiley's own downfall in another way. If this is the end of the Smiley stories (and the author does seem to have painted himself deliberately into a corner), it is an appropriately ambiguous conclusion to a series that has dealt splendidly in ambiguities from the beginning.

In terms of style and action, Smiley's People differs slightly from some earlier episodes in the series -- and those who have decided that The Spy Who Came In from the Cold or Tinker, Tailor, Soldier, Spy or The Honourable Schoolboy is the ultimate model for all books of this kind may detect a small falling-off in quality, as though the author has finally wearied of his subject or feels he has said it all. The opinion is arguable either way; le Carre does sometimes get involved in people at the expense of smoothly intricate plotting in this volume, but the gains in vivid portraiture may outbalance the losses in "what happens next?" interest. And those who decide that it is not quite top-drawer le Carre should also note that this author's second-best is still better than almost anything else in the field. CAPTION: Illustration, no caption, By Michael David Brown For The Washington Post; Picture, John Le Carre, Copyright (c) Andreas Heumann