The Turn of the Key by Ruth Ware is a gripping locked room mystery that follows a young woman named Rowan Caine, who takes a job as a live-in nanny at a remote Scottish estate. The book is structured as a series of letters that Rowan writes to a lawyer, pleading her innocence in the murder of one of the children she was hired to care for.

One of the most notable aspects of the book is its use of a modern technology as a plot device. The estate is outfitted with a sophisticated home automation system, which adds an extra layer of tension to the story. The technology seems to have a mind of its own, causing doors to lock and unlock, lights to turn on and off, and music to play without explanation. This creates a sense of unease that permeates the entire book.

The setting of the remote Scottish estate is also expertly crafted, with Ware creating a sense of isolation and claustrophobia that heightens the tension of the mystery. The house itself is described in vivid detail, with secret passages, hidden rooms, and ominous features that add to the sense of foreboding.

The characters in the book are also well-drawn and distinctive. Rowan is a complex and flawed protagonist, struggling to navigate the challenges of her job while also dealing with her own personal demons. The other characters at the estate, including the children she is caring for and the other employees, are all suspects in the murder and are fleshed out in detail.

The mystery itself is expertly plotted, with Ware weaving together a complex web of clues and red herrings that keeps the reader guessing until the very end. The use of the home automation system as a plot device adds an extra layer of intrigue, as the reader is left to wonder if the system is malfunctioning or if someone is manipulating it for their own purposes.

The Turn of the Key is a compelling and atmospheric locked room mystery that will keep readers on the edge of their seats. The book offers a fresh take on the classic whodunit, incorporating modern technology and psychological exploration to create a complex and satisfying story.