Milan Kundera's dazzling novel "The Book of Laughter and Forgetting," published here in 1980, was a revelation to xenophobic readers. All preconceived notions of what a "Czech novel" might be were confounded by this extraordinary work, at once political and philosophical, erotic and spiritual, funny and profound. As for the author's intentions, Milan Kundera has commented (in a conversation with Philip Roth) on the peculiar hospitality of the novel form: "Ironic essay, novelistic narrative, autobiographical fragment, historic fact, flight of fantasy: The synthetic power of the novel is capable of combining everything into a unified whole like the voices of polyphonic music."

Now we see that "synthetic power" splendidly at work in Milan Kundera's new novel, "The Unbearable Lightness of Being."… It centers on the connected lives of two couples. Tomas is the most promising young surgeon at his hospital in Prague. He is also an "epic womanizer" and collector of women. Among the dozens he has slept with, his wife, Tereza, and his mistress, Sabina, represent fidelity and betrayal, the opposite poles of erotic possibility….

In the binary universe of this novel, it is not only lovers who are paired and repaired with old and new partners. Being itself is divided into pairs of opposites. Fidelity and betrayal, soul and body, political oppression and personal feeling balance and modify…. Most of all, however, life is both "light" and "heavy." Sometimes we make the "heaviest" life choices in the lightest and most accidental way. Sometimes, recognizing the transitory quality of even the gravest burdens, we experience "the unbearable lightness of being."

"The Book of Laughter and Forgetting" was a series of episodic variations on a theme. "The Unbearable Lightness of Being," a work of larger scale and complexity, is symphonically arranged, so that thematic events are constantly enriched by smaller phrases and motifs. The theme of political "necessity"—centering on the Russian invasion of Czechoslovakia in 1968—is echoed in many small allusions. The "necessity" of Tomas's love for his wife Tereza is signaled by the fact that at the beginning of their acquaintance she is clutching a copy of "Anna Karenina."

The symmetrical composition of that novel is not merely "novelistic." The author explains that we all compose our lives like music, turning chance occurrences into permanent motifs. In the polyphonic music of this novel, Mr. Kundera points out that each voice is singing its own version of two motifs Beethoven named "the difficult resolution": "Muss es sein? Es muss sein!" ("Must it be? It must be!")

Necessity is a less memorable theme in Mr. Kundera's work than sexuality. He has observed elsewhere that "a scene of physical love generates an extremely sharp light which suddenly reveals the essence of characters and sums up their life situation." Certainly there is no wiser observer now writing of the multifarious relations of men and women….

Mr. Kundera is not alone in possessing a philosophical sense of humor, a liking for human crankiness, and a political sensibility. What distinguishes him from, say, Kurt Vonnegut? Perhaps one judges Mr. Kundera the better novelist in homage to his country's gallant sufferings—a form of romanticism, incidentally, that the author regards with some amusement. I think, however, that Milan Kundera is the more durable because his world view is the more open. However schematic his "double exposures"—laughter forgetting, heaviness lightness, soul body—his novels do not move according to formula, but acquaint the reader with the complex variations of an intelligence both speculative and playful. "The Unbearable Lightness of Being" is his best novel yet.