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
When she reproached him, the first time they made love, about his acting too intellectual, he had tried, starting the next day, to correct that impression by showing spontaneous, unbridled passion. (I.9.4)
We have to understand that the term "intellectual" carries a negative connotation in Communist Czechoslovakia (as it sometimes does in the United States, too, unfortunately). There's such a strong bias against intellectualism that the word "intellectual" becomes one of the deepest insults one can dish out. (And it's no surprise since the thing with intellectuals is that they're smart enough to see through Communist propaganda—and that makes them dangerous.)
In this case, Mirek gets zinged about his sexual prowess. He can't let it be, of course, and he tries his best to impress Zdena. But she's having none of it. The chemistry just isn't there between them.
Quote #2
Some years ago, Marketa had urged him to make love in a threesome with her and a mistress of his she was jealous of. Her proposal made him dizzy with arousal! But the evening scarcely gave him any pleasure. On the contrary, it was a horrible effort! (II.8.7)
Poor Karel. He just can't get no satisfaction in his love life, no matter how enticing the opportunities seem. His major problem? Total self-absorption. Karel harbors a longstanding inferiority complex because he couldn't make love with his mother's beautiful friend when he was 4 years old (yeah, we can't make this stuff up), so most sexual encounters leave him feeling empty and wanting more. It's not until a Mrs. Nora lookalike appears that Karel can feel sexual gratification. As for the real women in his life? They'll just have to resort to each other.
Quote #3
During that brief rest period, it wasn't Mrs. Nora he was seeing but his old girlfriends, his life's witnesses Marketa and Eva, and he felt like a great chess player who has conquered opponents simultaneously on two chessboards. (II.11.17)
Karel's ego is totally gratified by having had sex with his wife and mistress at the same time. He's got that cat-that-ate-the-canary sense of satisfaction, and he can't help crowing about it. In his mind, he has just done something wonderful: he's conquered the space-time continuum to make love with a beautiful woman from his infancy. It's quite pervy, really, and neither Marketa nor Eva is particularly impressed.