The Unbearable Lightness of Being signals in the first chapter that it is a philosophical novel--it begins with the narrator ruminating on the "myth of eternal return" and the contrasting concepts of lightness and weight. The narrator periodically reinserts himself throughout the novel, making clear that the characters are fictional creations being moved through the "plot" to make a point about the effects of communism or the difficulty of identifying which side of such pairs as lightness and weight, happiness and sorrow is the positive side. He also riffs on such matters as kitsch and what the act of defecation shows about God.
The primary characters in the story are Tomas and Tereza, a married Czech couple living through the Prague Spring, the Soviet invasion of 1968, and the aftermath of these events. Tomas is a skilled surgeon, who meets Tereza by accident (he is filling in for his ill boss at a conference and dines in the restaurant where she is working as a waitress). They marry, but this does not change the fact that Tomas is an unrepentant womanizer. After the Soviet takeover, Tomas is targeted because of an article he wrote in a paper run by intellectuals. Officials put pressure on him to repudiate the article, but he recognizes that his career is ruined whether he stands by his article or repudiates it. He gives up medicine and becomes first a window washer and then a worker on a commune. Tereza becomes a successful photographer, but she too loses her job and returns to waitressing. Terrible dreams haunt Tereza, and her husband's infidelity tortures her. Only her dog Karenin brings her any real joy. Shortly after the dog's death from cancer, Tereza and Tomas die in a truck accident.
Throughout the book, occasional sections are devoted to the artist Sabina, one of Tomas's many mistresses, and a lover she takes after emigrating to Geneva, Franz. When she breaks up with Franz, he quickly finds a new woman (one of his university students), but he holds Sabina in almost religiously high regard--he judges his actions by how she might evaluate them. When he joins a protest in Southeast Asia, he is accidentally killed, ending an essentially meaningless life in a meaningless way. After moving to the United States, Sabina dies, too, but I don't even remember how.
Of course, all characters in novels are fictive, but when the author acknowledges that they are merely stick figures designed to make his point or provide a backdrop for his musings, my interest in them diminishes. Yes, Kundera is making points about communism, about love, about reality--whatever. I'd rather read an essay explicating those points than this novel (acknowledging that perhaps I am just hopelessly shallow).
Favorite passage--None really