All I can say is…wow! What a ride! I don’t want to say too much and spoil the fun. This starts slow, and gets creepier, and the pace picks up, and then it really races at the end (a bit like a train picking up speed). I listened to this from audible.com and it was a perfect book to accompany me on my commute. The three female narrators were voiced by 3 actors which added to the tension. You don’t know until the end who’s a reliable narrator and who isn’t. Very clever.
I’m sure this will be adapted for the screen, but I highly recommend you read it first.