The Fiancee by Kate White

 Summer is an actress (who wishes she has had more professional success) married to Gabe, one of the 3 sons of a wealthy family. All 3 sons and their respective wives head to the family's country estate for a week of summer vacation. Summer is surprised to find that brother Nick has brought his new girlfriend--Hannah (a fellow actress that Summer had met a few years earlier). When Summer reminds Hannah that they have met, Hannah says Summer must have mixed her up with someone else. But Summer knows she's right and wonders what Hannah is up to. Then Nick and Hannah announce their engagement (hence the title The Fiancee). It turns out that Summer is not the only one who is not a big fan of Hannah's. Then someone dies and Summer is convinced Hannah had something to do with it--though she cannot convince her husband (who thinks she is jealous of Hannah's more successful career). The tension ratchets up when yet another body is found on the grounds. This was a good psychological thriller with some interesting twists and turns. And definitely a quick read. I polished the whole book off in one afternoon in the park.