oooh, goodreads choice awards semifinalist for best mystery! what will happen? 
 well, that was fast... 
 i can't remember the last time i blitzed through a book as quickly as i did this one (*EDIT - yes, i can - it was Gemina). i had about fifty pages to go in the book i was reading (The Three Heretics) which i knew would not be enough to last me my whole day, and i didn't want to carry TWO books into the city like some donkey, so i grabbed this one on my way out the door, and by the time i went to bed that evening, i had finished it with time to spare, and with time to finish those final 50 pages. ordinarily, on my way to work in that sleepy time of the morning when the sun's not even up yet, i use my subway time to doze a little over my book, but with this one, i was too sucked in to nap, which is pretty remarkable. 
 quickplot - cass is a teacher living in a lovely, but isolated, house in a small english town with her devoted husband matthew. one violently rainy night, driving home to matthew after an end-of-year party, cass takes the shortcut home, despite matthew's insistence that the path through the woods, with no mobile signal, would be too dangerous in the storm. she is nearly home when she sees a car pulled over on the side of the road with a woman inside. the rain makes it too blurry to see much, but cass is concerned that the woman might need help, so she pulls over. she waits for the woman to take advantage of her good samaritinism, but as the minutes tick by with no action or signal from the woman, cass becomes increasingly paranoid, imagining all the urban legend scenarios of a hitchhiker in the backseat of the woman's car, and she bounces. the next day, it is all over the news: the woman she saw was found murdered in her car right where cass left her. even worse, it was a woman with whom she was acquainted, and she feels guilty for having left her the way she did. however, not wanting to admit to matthew that she took the shortcut he warned her against, she suffers her guilt in secret. she is also hiding another secret from her husband; her recently-deceased mother suffered from early onset dementia, and cass has herself been experiencing episodes of memory loss, which the stress of the murder intensifies. between the weight of her secrets and the fear that she will end up as helpless as her mother, cass' mental state worsens as the long empty days of summer stretch on; she's preoccupied, forgetful, paranoid, and she begins to suspect she was seen by the killer that night, and is his next target. 
 it's one of those books that, once it starts, just never lets up, and cass' unraveling is a wonderful trainwreck. apart from one necessarily exposition-heavy chapter at the beginning, the chapters are wicked short, which speeds up the pacing, and with threats both internal and external, killer and mental breakdown (because the book's title is doing two jobs, yeah?), it's my favorite combination: suspense and an unreliable narrator. 
 although only one star separates this from Behind Closed Doors in my gr ratings, i liked this one considerably more. it's much more plausible, although it does rely on a genre-standard that i've come to accept as par for the course in psychological suspense, even as it irritates my common sense. (view spoiler)[everyone who is close to you is eeeeevil and are all masterminds at concealing it (hide spoiler)] 
 but, from a thriller standpoint, it definitely delivers. 
 i recently read Gone Without a Trace, which delivered a similarly claustrophobic reading experience, as you get immersed in the perspective of a character whose world seems to be disintegrating and can no longer trust their own mental faculties. which would be horrifying in real life, but delivers a chillingly pleasant intensity when you're safely reading. 
 more like this, please!