The Forever Summer by Jamie Brenner

When successful lawyer Marin Bishop is contacted by a woman named Rachel saying they are sisters, she is skeptical, because her parents have been married for many years. However, when Marin is fired from her job after having a relationship with a co-worker, she takes Rachel up on the offer to travel to Provincetown to meet their grandmother, Amelia, who runs an inn on the island. They are joined by Marin's mother, Blythe, who wants to support her daughter with this sudden news (and also get away, since her husband, Kip, has just asked for a divorce). The Forever Summer follows the stories of Marin, Rachel, Blythe, Amelia and her partner, Kelly, as they come to terms with relationships both new and old. A great beach read, especially for those who love Elin Hilderbrand.