Thriller.
Psychological Thriller.
I was certainly thrilled and pleased with the conclusion!
You should read it if you want to spice up your romantic relationship or marriage and give it longevity. (ha ha, I'm only kidding...if you are!)

It's actually a good book.
I definitely enjoy the way that the author wrote Amy.
It does make me laugh the way she wrote Nick Dunne, spasms of laughter were continuously emitted by me!

I know this is a book review, but, admittedly, the movie, was I daresay, as equally riveting and somewhat true to the book.
Rosamund Pike portrayed Amy well, and I think Ben Affleck was a good Nick.
I suppose David Fincher was (is) a good director as well.

Whether you watch the movie or read the book, you won't be disappointed.
Go for it.