I loved, loved, loved Lisa Jewell's "The Girls in the Garden" (also called "The Girls" in some editions). Marketed as a character-driven thriller (more of a character-driven mystery), it's a page-turner that makes you think about deeper issues and fall in love with the characters.
Imagine that you live on a picturesque communal garden square, an oasis in urban London where your children run free, in and out of other people's houses. You've known your neighbours for years and you trust them. Implicitly. You think your children are safe. But are they really? On a midsummer night, as a festive neighbourhood party is taking place, preteen Pip discovers her thirteen-year-old sister Grace lying unconscious and bloody in a hidden corner of a lush rose garden. What really happened to her? And who is responsible?