Fiction by Delia Ephron.
When I typed the author's name above, I accidentally put "Nora Ephron" first, instead of the correct sister's first name. I'll bet poor Delia gets that a lot. And, interestingly enough, it looks like Delia is the more prolific writer, although Nora seems to be more well-known. But I digress.
This was another strange book, more of a character story than a plot-driven novel, although some things do happen. It is about two couples (one with a child) who go on vacation together, with the odd complication that none of them actually seem to like each other that much, except the ones who used to date but are now married to other people.
Yes, we actually have a woman here who says to herself, "I think it would be nice to take a vacation abroad with my husband and child, and I believe we should take along my husband's ex-girlfriend and her husband! Just for fun!" Not surprisingly, trouble arises on this trip...