Twenty-five years ago, Mirek fell in love with Zdena, a stupid, ugly woman; it lasted about three years, and now he wants to forget.

Seventy years ago, Tamina's father lived on Cernokostelecka Avenue -- the Avenue of the Black Church -- in Prague. After World War I, he married and lived on Marshal Foch Avenue. Tamina was born on Schwerin Avenue during World War II, when the Germans were occupying the city, but she spent her childhood on Stalin Avenue. At the time of her marriage, she was living on Vinohrady (Vine-yards) Avenue. "All the time," says Milan Kundera, who makes the story of Tamina the keystone of his latest masterpiece, "it was the same street; they just kept changing its name, trying to lobotomize it."

Tamina's husband has died. She wants to remember him but has trouble; she is an exile, and most of the key documents were left behind at home.

More than 31 years ago, in February 1949, the Communists took power in Czechoslovakia -- "not in bloodshed and violence," Kundera reminds us (he was there) "but to the cheers of about half the population. And please note: the half that cheered was the more dynamic, the more intelligent the better half."

Being dynamic and intelligent, they later changed their minds but found it was more difficult to change their situation -- to wipe out and forget their mistake. When they finally managed to do it, in the "Prague Spring" of 1968, Russian tanks rolled in. Forgetting is not so easy when ugly memories are reinforced by tanks. It is easier when the tanks are on your side; many of those who helped Czechoslovakia to become a workers' paradise and later changed their minds have been erased -- banished from memory, airbrushed out of photographs and edited out of history books.

Mirek and Tamina are images of Czechoslovakia; so is the street with many names. Milan Kundera, for that matter, is an image of Czechoslovakia. He was still a citizen of that unhappy nation when his earlier masterpieces, "Life Is Elsewhere," "Laughable Loves" and "The Farewell Party," were published. Now he lives in Paris, and his Czech citizenship was revoked (that is, part of his past was erased) after the publication in France of "The Book of Laughter and Forgetting." It was a completion of the process begun after the Russian invasion of 1968, when his books disappeared in Czechoslovakia. He is naturally concerned about the practice of revising the past, and he makes it one of the themes in his latest novel -- which is really a collection of short stores, liberally seasoned with fragments of his country's history and his own biography.

How does Kundera dare to describe as a "novel" a book which is clearly a collection of seven short stories and random personal observations? He explains it himself in one of those observations -- a bit of nonfiction, cannily embedded in his fiction, which draws on his experience in earlier life as a musician and the fact that his father was a noted pianist. The symphony, he says, is "a musical epic . . . a journey leading through the boundless reaches of the external world, on and on, farther and farther." Variations are also a journey, not through the boundless space outside but into a second infinity, "the infinity of internal variety concealed in all things." It is "the form of maximum concentration," enabling the composer "to limit himself to the matter at hand and go to the heart of it. The subject matter is a theme, which often consists of no more than 16 measures. Beethoven goes as deeply into those 16 measures as if he had gone down a mine to the bowels of the earth."

Call it a novel or any other convenient title; what Milan Kundera has written is a set of fantastic variations on a political theme -- acutally a variety of themes, though they might all be reduced to a single note: manipulation. Two primary themes are mentioned in the title, but there are many more; they blend into one another and resonate together, a motif of childhood connecting with motifs of happiness and lack of memory and aimless activity and ultimately a theme of death. The theme of privacy versus socialization merges into the theme of memory and its manipulation, which are ground bass notes in this composition, for memory is a large part of what makes each of us an individual, what makes a society a culture -- and that, too, is part of the book. "The first step in liquidating a people," a friend tells Kundera, "is to erase its memory. Destroy its books, its culture, its history. Then have somebody write new books, manufacture a new culture, invent a new history. Before long, the nation will begin to forget what it is and what it was. The world around it will forget even faster."

Kundera's variations happen in the reader's mind as much as on the page, for they are often variations of resonance and no two people resonate in quite the same way. And that, too, is one of the points of his book -- but another is that things which seem opposite after often essentially the same.

Consider Mirek: A vigorous critic of his government and its attempts to revise reality, he keeps meticulous notes of how things actually happened as an act of defiance and resistance. But Mirek is ashamed of an old love, and is trying to recover and destroy some old love letters. The chief difference between Mirek looking for letters, and what the secret police do, is that Mirek fails and the police succeed.

"Mirek," Kundera says, "is as much a rewriter of history as the Communist Party, all political parties, all nations, all men. People are always shouting they want to create a better future. It's not true. The future is an apathetic void of no interest to anyone. The past is full of life, eager to irritate us, provoke and insult us, tempt us to destroy or repaint it. The only reason people want to be masters of the future is to change the past. They are fighting for access to the laboratories where photographs are retouched and biographies and histories rewritten."

Kundera, as an artist, has the key to such a laboratory, and one of the ways he uses that key is to seek mastery of his past. He writes variations on that past, but his purpose is not to alter or destroy it; rather, through these variations, he seeks to understand it, to penetrate its reality to the microscopic level, and to share with the rest of us what he has found.

In "The Book of Laughter and Forgetting," he has succeeded.