Nine Perfect Strangers by Liane Moriarty

Really Moriarity is mailing it in with this one.  Nine quirky people at a luxury spa operated by the messianic and sinister Masha.  You might care about the lives and personalities of these people as they are gradually revealed under the most terrifying of conditions - or they might just seem like whiners.  Masha made have had a plan to improve this lot but it doesn't include rest and relaxation.  I kinda thought the whole premise was lame.