The Housemaid by Freida McFadden

From behind closed doors, she sees everything. Every day I clean the Winchesters' beautiful house top to bottom. I pick up their daughter from school. And I cook a delicious meal for the whole family before heading up to eat alone in my tiny room on the top floor. I try to ignore how Nina makes a mess just to watch me clean it up. How she tells strange lies about her own daughter. And how her husband, Andrew, seems more broken every day. But as I look into Andrew's handsome brown eyes, so full of pain, it's hard not to imagine what it would be like to live Nina's life. The walk-in closet, the fancy car, the perfect husband... I try on one of Nina's pristine white dresses once. Just to see what it's like. But she soon finds out... and by the time I realize my attic bedroom door only locks from the outside, it's far too late. But I reassure myself: the Winchesters don't know who I really am. They don't know what I'm capable of ... Book 1 of 3!