You Were Made for This by Michelle Sacks

Doting wife, devoted husband, cherished child. Merry, Sam, and Conor are the perfect family in the perfect place. Merry adores the domestic life: baking, gardening, caring for her infant son. Sam, formerly an academic, is pursuing a new career as a filmmaker. Sometimes they can hardly believe how lucky they are. What perfect new lives they’ve built.

When Merry’s childhood friend Frank visits their Swedish paradise, she immediately becomes part of the family. She bonds with Conor. And with Sam. She befriends the neighbors, and even finds herself embracing the domesticity she’s always seemed to scorn.

All their lives, Frank and Merry have been more like sisters than best friends. And that’s why Frank soon sees the things others might miss. Treacherous things, which are almost impossible to believe when looking at this perfect family. But Frank, of all people, knows that the truth is rarely what you want the world to see.