The entirety of this book is remarkably unsettling.
This is a psychological thriller with the emphasis on psychological. Every bit of the writing, the characterization, even the setting suits the mood of the story. It is cold and bleak. Rooting for main character Marta becomes remarkably easy very early on, given how isolated she is, but trusting her completely never feels quite right. She probably isn't crazy, except she certainly acts that way sometimes. And it is hard to believe that what her husband is telling her is true, except that isn't anything else even more ridiculous?
One of the main reasons I enjoyed this is because things are not handed to you too quickly. Figuring out what is going on is a tricky business, and it's hard to make a clear judgement call. Are Marta's pills confusing her, or is being off the pills confusing her? What on earth is actually going on?
Many of the other characters are not terribly likeable, though that in itself is part of the dark charm of this. How much leeway does one give Marta for simply appearing, as the narrator, more likeable than those surrounding her?
There probably end up being more questions than answers in this, but that's not necessarily a bad thing in my opinion. There are fewer sudden and shocking surprises in this than in the big-name psychological thrillers from the last few years, but none of them manages to maintain this atmosphere. It's more reminiscent of The Yellow Wallpaper than anything else, although I won't argue it is quite on that level. It is an intriguing story, though, and well worth the read.