The title is absolutely great.
One of the classics, no question.
RIP.
If you read a lot of his books they all turn out to be pretty similar imho, but it fit my vibes when I was like 18.
Another book that's great for re-reading is "The master and Margarita", pretty layered in terms of the different experiences you can have reading it.
And, I agree: the plot is barely worth mentioning. In fact, I once started watching the movie and stopped halfway through because it was just so banal and uninteresting. The great stuff is in all the little observations and considerations that aren't really part of the "story".
It’s also, of course, a very political novel in its depiction of life in the Soviet Bloc and of popular movements. It’s a very pointed critique of collectivism.
This. I don't get the sense that Kundera himself is advocating for either lightness or weight. The novel asks a question that's as much philosophical as it is psychological, and the beauty lies in the question itself rather than any answers.
To quote Kundera: "On the surface, an intelligible lie; underneath, the unintelligible truth."
The novel contains various asides where the author says what the book is about and it's not this.
Heaviness and lightness are two different attitudes towards life. Lightness is not committing to anything, chasing experience, infidelity, pleasure, and so on. If anything, the novel comes down on the side of heaviness: tenderness, commitment, marriage, having a dog even though it will die, etc.
It isn't really too much of a novel because it has a very thin plot with very little drama or tension. It is more like a deep reflection. But it is very good.
The book's perspective on human condition is very cynical. My understanding, when I read it, is that by "unbearable lightness" what the author means is that we are absolutely irrelevant and the whole idea of "meaning of life" is just pathetic.
Yeah, I know: I sound like an atheistic teenager. But, please, don't get fooled. Kundera wrote a billion times better than me. He deserves to be read, even if I sound childish.
If you like Albert Camus you'll love Kundera (and vice-versa).