Truly madly guilty by Liane Moriarty
The barbaque that Clementine, Sam and their children, with their friends Erica and Oliver went to at their neighbors Vid and Tiffanys. All of the “responsible” adults have secrets that become difficult to cope and live with after the barbaque.
A compelling book that keeps you guessing till the very end.
Also by Liane MoriartyThree wishes (audio book)