This is a rough premise for a book - her fiancee was found shot in dead with their girlfriend. "Their" because they were in a polyamorous relationship with her. 

They connect after the funerals/investigations and bond on the hurt and trauma they face from the cheating and death of their partners. 

This book didn't exactly hit the right marks for me. I think the relationship between Shaw and Brook was underdeveloped, and Vaughn and Brook was too rushed. I would've liked more exploration of Shaw's commitment issues, why he wants to stay in Cape Cod instead of moving in with Vaughn, the topic of marriage, etc.