I watched Charlie Kaufman's film of the same name before reading this. While I found Kaufman's film to be too impenetrable and obtuse, I can see why he would have wanted to adapt the novel.
As a debut novel, it's really assured and confident in what it is trying to do. Iain Reid's story is compelling in how it shifts what you know about characters as you read it. There are moments of genuine terror in this novel. No cheap, jump scares here. The way he describes small details in everyday life is well captured, and help the book feel grounded in reality for when things get more surreal later.
First book I've read in a long time where the discussion questions at the end weren't tracked on garbage, but invoked thoughtful review of the book. An excellent debut. I look forward to more from Mr. Reid.
I'd recommend reading it in as few sittings as you can, so that you can have it linger with you after the fact properly.