Rush of Blood by Mark Billingham

Mark Billingham usually writes the "DI Tom Thorne" suspense/mysteries, but his last two books have been standalone with Tom just peeking in at the end.  In this book, three British couples meet and hang out together at a Florida resort.  They become somewhat friends, eating, drinking, and sunbathing together. A single woman with her handicapped daughter, Amber Marie, is often at the pool as the girl likes to swim.  On their last day, Amber Marie is reported missing.  Her mother frantically searches for her to no avail.   Detective Jeff Gardner is assigned to the case.  Statements are taken from everyone at the resort, and the three couples are allowed to return home on schedule.  The poor mother stays in a nearby hotel for months until her daughter's body is found in the mangroves by fishermen.
Once Angie and Barry, Marina and Dave, and Sue and Ed return to England, they decide to meet for dinner at each other's homes in an attempt to remain friends.  The first dinner is at Angie and Barry's home.  From the beginning, the disappearance of Amber Marie hangs over them and is a topic of discussion.  Everyone is uncomfortable, and as the dinners continue, it is evident that they all have secrets and that they all lied to the Florida detective.  As they continue to meet, we get to know each of the couples as individuals and the secrets they hide.  When another girl is found dead in England and there are similarities to Amber Marie's killing, a local detective begins to tie the two murders together.  The tension ramps up until it explodes!

Mark Billingham's books are character and plot driven, and these standalones can be read quickly.