"It's only words, and words are all I have, to take your heart away." —Bee Gees
I think the dual timelines don't really work in this novel. The chapters switch between the ill-fated 'Day of the Barbecue' and two months afterward until halfway through the book. Obviously this is intended to build suspense but Moriarty spends too long skirting around what actually happened at the barbecue while continuing the present narrative and discussing the consequences, and at some point I just wished she would reveal everything already.
There seems to be so much hidden bitterness between the characters -- between husband and wife, between friends, between one couple and another. It was uncomfortable to read but I guess that's the point of the story: to uncover what's buried beneath the layers of people's relationships (which Moriarty does exceptionally well), and it's not always pretty.