How we cite our quotes: (Part.Chapter.Paragraph), with the exception of Part V, which runs (Part#. "Short Title". Paragraph). Part V has no numbered chapters—only title headings.
Quote #1
He had needed at all costs to prove to himself that it was not his weakness and poverty that bound him to this woman, but love! And only a truly immense passion could justify an affair with such an ugly girl. (I.13.2)
Mirek seeks out his old love letters to Zdena because he wants to have control of his past. Really, he wants to rewrite history so that it makes better sense to him and everyone else who looks at it. The problem? Zdena is not a pretty woman. Not in the least. So Mirek feels he needs to find a plausible reason for having had an affair with her. And why would a man being pursued by the secret police care about such a tiny detail? Your guess is as good as ours.
Quote #2
...she was the only woman who wasn't annoyed by Karel's love for Marketa. "Your wife should understand that you love her but you're a woman-chaser and your chasing is no threat to her. But no woman understands that. No, there isn't a woman who understands men," she added sadly, as if she herself were a misunderstood man. (II.5.13)
Eva's a special lady. She calls herself a "man-chaser" and feels that all sexual conventions are stupid and meaningless. Her version of love extends only to sensuality and friendship; it has no room for things like commitment and fidelity. Karel benefits immensely from this ideology, as he's a woman-chaser. But for his wife, Marketa, something's gotta give. She actually loves her husband, but she can't take his free-love ideas. It's actually Eva who solves Marketa's problems: she offers affection and intimacy to Marketa, who finds she can bear her husband's philandering very well if she's with somebody who's really into her.
Quote #3
...every love relationship rests on an unwritten agreement unthinkingly concluded by the lovers in the first weeks of their love. They are still in a kind of dream, but at the same time, without knowing it, are drawing up, like uncompromising lawyers, the detailed clauses of their contract. (II.6.11)
Kundera comments on Marketa and Karel's relationship specifically, but he extends the analysis to all lovers. He hypothesizes that lovers fall into roles very early in a relationship and then find themselves having to stick to those roles forever. In this case, Marketa finds herself on the losing side of the bargain. She gets to play the role of loving and wronged wife—it's not something she loves. When Eva comes along, Marketa gets the chance to rewrite that role for herself.