Dinner Party, by Tracy Bloom, is centred around an unexpected guest to a dinner party. The summary says:
Three couples take it in turns to host a monthly dinner party.
Beth, Sarah and Marie have been friends forever. Now they are grown up, with busy lives, busy husbands, busy kids... but they still find time to meet up over dinner once a month. A cosy, comfortable gathering of happy couples - or so they thought.
Until one night, someone brings along a last-minute guest whose wife has just left him. Simon is standing on the doorstep in floods of tears. While the women do their best to console him, their husbands feel the need to mark their territory.
And as Simon becomes more involved with the group, his presence changes everything these three couples thought they knew about each other, leading to a final dinner party that no one will ever forget." Dinner Party is out in September 2018.