I'm currently reading this for the second time, and falling in love with it all over again.
Without spoiling the storyline, it's basically set in the 1960s and follows a woman in high(ish) English society who has an affair. (There's also a storyline of a woman who's having a modern-day affair, but that's not nearly as interesting.) Though there are a lot of differences, it's quite reminiscent- to my mind at least- of Anna Karenina; I watched the film recently, now aiming to read the book!
Anyway, something that really intrigues me about both storylines is the way that the men who have been cheated on refuse to break up with their partners; they give them chance after chance. It's a totally different world to now- if someone in a relationship so much as looks at someone else, their respective partner seems to instantly scream, 'Go, and never darken my towels again!!'. I think I prefer the old way, where people stayed together and tried to reconcile. It seems more like 'love' to me.