My ONLY objection to this book was the title. When I read the cover, and saw that it was about a couple who are lost at sea, I assumed "the castaways" referred to them, and that they would eventually be discovered alive. I expected a story that flashed back and forth between the devastated family on land and the desperate couple at sea. But that idea was immediately debunked. I'm not spoiling it for you by saying that the couple at sea is definitely dead. They are dead on page one, and there's no mystery involved, except for what happened to cause their deaths.
"The Castaways" refers instead to the self-imposed nickname of the group of couples that formed a tight friendship circle on the island of Nantucket. Greg and Trish, the lost-at-sea, were two of the eight. The book is about how the remaining six each find their own ways to move on after Greg and Trish's deaths. It's a close-knit, sometimes incestuous bunch. The eight took several vacations together; two of them, including one of the dead, were involved in an affair; two had previously dated and even lived together before their separate marriages; and all of them have a certain degree of attraction or feeling for at least one of the others. The book explores all of those ties, the marriages and the friendships, the healthy and the unhealthy relationships, including the ties that bind the living to the dead. There's a lot of reminiscing and a lot of trying to move forward, and everyone deals with their grief in a unique but completely apropos way. All of the characters are equally enjoyable to read about, which I think is rare for a multi-perspective book, and despite its morbid framing, the book actually feels very heartwarming.
I highly recommend this for your beach bag- it's definitely my favorite Elin Hilderbrand thus far.