Although this isn't considered a great book, I really liked it. I think it's because I think our culture is filled with a lot of sexual ambiguities. Girls kiss each other for attention, threesomes aren't abnormal and I think in general people don't have a lot of hope for the regular marriage (or committed relationship, or whatever).
I think this book does a good job at saying "Ok, so what if all this stuff is true, what does this mean a relationship looks like?" We see two couples subject their marriage to sexual escapades (mostly together, but not all) and I think we see what feels necessary to the characters feels a lot more like self-indulgence.
I wouldn't say it's a great book, I didn't find I cared about the characters, but I did feel the emotional acrobatics they go through resonated for me. We can be flawed and be forgiven, but it's where we lie to ourselves and lie to those we care about that we really get hurt.
Just finished this book. While reading it I had the sensation of reliving every stressful childhood moment ever. Every moment where you suspected maybe your parents were flawed and that it was possible that they were making a mistake right at that moment -- and there was nothing you could do about it. Intertwined with that sensation is the sensation of reliving all your own stupid mistakes, but right BEFORE realising you're repeating the mistakes you've seen others make.