Truly madly guilty - Liane Moriarty

Six responsible adults. Three cute kids. One small dog. It's just a normal weekend. What could possibly go wrong?

Sam and Clementine have a wonderful, albeit busy, life. If there's anything they can count on, it's each other. Clementine and Erika are each other's oldest friends. But theirs is a complicated relationship, so when Erika mentions a last-minute invitation to a barbecue with her neighbors, Tiffany and Vid, Clementine and Sam don't hesitate. Having Tiffany and Vid's larger-than-life personalities there will be a welcome respite. Two months later, it won't stop raining, and Clementine and Sam can't stop asking themselves the question: What if we hadn't gone?