THERE ARE MOMENTS in life, moments whose very significance we often perceive only much later, moments when a gesture, a word, a sentence can entirely change the course of the years that come after it. "To follow once the false ringing of the night bell," Kafka mused about such a moment in life. This moment in the life of young Ludvik is the core of Milan Kundera's novel The Joke. The novel, completed in 1965 and published two years later, had a short and successful life in the heady and reckless days of the Prague Spring, preceding August 21, 1968. Then, immediately after the Russian invasion of Czechoslovakia, it was banned, removed from all public libraries, erased from the history of Czech literature. Its author, considered one of the initiators of the "counterrevolution," was deprived of his right to work, and later forced to emigrate.

In the late '60s the novel's English translation appeared in London and New York; this translation was a truncated edition, the order of chapters was reversed, many pages were omitted. Now, in an excellent translation by Michael Henry Heim, Americans finally can read the complete novel. And it is, as Louis Aragon has written in his moving foreword to the French edition, "one of the greatest novels of the century."

Milan Kundera himself calls The Joke a "love story." But if it is truly one, then it is a love story wrapped into a veil spun of that characteristically Czech fabric of self- mockery, then it is embroidered with that which the Czechs do so well: laughter through tears. There is no melodrama here, although the novel tells of a life thoroughly disrupted, of illusions thoroughly shattered. Even the idea of revenge, which had sustained Ludvik and ultimately made him survive, in its actuality proves thoroughly futile and grotesque.

The moment which gives Ludvik's life a completely different direction is essentially a moment of playfulness. A Party member, one of the promising young cadre of the Communist elite, he sends his girlfriend comrade a postcard, poking fun at optimism, the healthy atmosphere, and, horror of horrors, hailing Trotsky. Dictatorships are notorious for their lack of playfulness and humor, and Ludvik's youthful joke turns out to have far-reaching results. He is expelled from the university and from the Party, is shunned and mistrusted by his former comrades, and spends years in an army penal battalion, working in the coal mines of eastern Moravia. During his years of labor he meets the girl Lucie, who attracts him and makes him happy by her bland ordinariness. Kundera movingly describes their first meeting and parting:

"We told each other the most ordinary things about ourselves, our confessions were short and to the point. When we reached the dormitory, we stood outside for a while under a streetlamp that bathed Lucie in light, and I found myself stroking not her cheeks or her hair, but the shabby material of her touching brown coat. . . . We agreed I'd send a postcard to let her know when I had my next leave and could see her. We said good night (without kissing or touching), and I walked away. After a few steps I turned and saw her standing in the doorway, not unlocking the door, just standing there, watching me. Now that I had moved away a bit, she could drop her reserve and allow her eyes (so timid before) a long stare. Then she lifted her arm -- like someone who has never waved, who doesn't know how to wave, who only knows that when one person leaves, the other person waves -- and did her awkward best to make the gesture."

When Ludvik loses Lucie, a long period of hopelessness and emptiness begins for him. When he finally realizes that he will never find her again, he becomes a coolly calculating operator. After his release in the post-Stalin thaw he conceives a plan to seduce the wife of one of his former comrades who had, by dogmatic statements and innuendoes, contributed much to his years as a nonperson. That he succeeds, after long scheming, succeeds in a moment when he is actually doing his adversary a favor, is the ultimate irony of his situation.

"My contemporaries and I merged into a single amorphous mass, corrupted by the same incomprehensible jargon, the same overpoliticized thought, the same anxieties . . . the same bizarre experiences from a dark and distant age. It was then I began to see that the similarity between myself and Zemanek was not limited to the fact that Zemanek had changed his views, brought them more into line with my own; it went much deeper, encompassing our destinies as a whole. . . . We were alike even when we were at each other's throats. I suddenly felt that if I were forced . . . to tell (her) the story of my expulsion from the Party, she would find it remote and too literary . . . the two of us would come off equally badly. . . . I saw our quarrel, which I had deemed so immediate and alive, sinking into the healing waters of time."

Ludvik's encounter with Helena, the wife of his former comrade, takes place against the backdrop of a folkloristic reenactment of an old Moravian legend. Kundera's favorite themes, of time and forgetting, and of individuals lost because of lack of memory, again come forth here. "I contemplated how I too (at this very moment) was caught up in that vast and inevitable forgetting. . . . A wave of depression came over me, not so much because the day had been futile as because not even its futility would remain; it would be forgotten with this table and the fly buzzing around my head and the yellow pollen scattered over the tablecloth by the flowering linden and the sluggish service so characteristic of the present state of theesociety I live in; and the society itself would be forgotten and all the errors and injustices that obsessed me, consumed me, that I'd vainly attempted to fix, right, rectify . . ."

There are only two decent men in the book. The first is a theologian, and Kundera's juxtaposition of him and the new state's efforts to create nonchurch celebrations (a baby's christening is called "a welcoming of new citizens to life") is brilliant. The second man, Ludvik's boyhood friend Jaroslav, a simple man who is capable of remembering and who suffers in his inability to forget, is stricken at the final enactment of the legendary Ride of the Kings. And only then, because of him, and perhaps for only a short time (we have no way of knowing, because the novel ends here), does Ludvik feel compassion. "I stroked his bald head and the long strands of hair mournfully trying to cover it and I realized with a shock that my journey home, undertaken to wreak vengeance on my enemy . . . was ending with my stricken friend Jaroslav (yes, at that moment I could picture myself holding him in my arms . . . carrying him, big and heavy as he was, carrying my own obscure guilt; I could picture myself carrying him through the indifferent mob, weeping as I went)."

Milan Kundera, in his preface, calls this "a book that tells of rape and has itself so often been violated . . . The ideologues in Prague took The Joke for a pamphlet against socialism and banned it; the foreign publisher took it for a political fantasy . . . and rewrote it accordingly."

May it now, with its second American publication, reach its place among the important books of our time, and may it not be forgotten. CAPTION: Pictures, Milan Kunderas Copyright (c) by Vera Kundera