I couldn't put Animal down. If nothing else, it's gonna grip you. But it just didn't do it for me personally, I do think a lot of that is personal taste, I think the narrator is a little too unreliable, and the really fast paced, short sentences jumped around too much. It's definitely not predictable, but you can see the outline of what is going to be revealed, just not what exactly happened; I wanted either more mystery around Joans past, or more character development from her. 

Please, please read the content warnings, and understand they are very graphic.