Basically, if you kill someone (is that the only way?) you end up with a literal animal manifestation of your guilt. On the plus side, they come with free magical abilities (like the main character’s ability to find lost things). On the down side, people know how you got your animal (your zoo) and discrimination is rampant.
It’s a really interesting concept; something that I haven’t quite seen anywhere else (The Golden Compass is vaguely similar, at least in the animal companions). And the world is just gritty and dark enough that it felt like a dark echo of what our world could be / have been. Unfortunately, a lot of details are left unclear. What exactly is the Undertow? How do people get which animals? What did the main character actually do to get her Sloth? How different are the animals from their wild brethren?
Unfortunately, as interesting as the world building is, the plot isn’t that great. I’ll admit, I actually stopped paying as close attention to what was going on about halfway through. Then some more things happened and the story was over and unfortunately I didn’t feel any particular urge to go back and figure out how we’d gotten from point B to point Z.
On top of that, I didn’t particularly care for the main character. When you open the first few chapters by writing scam emails and stealing people’s money, you know there’s a bit of an ethical conundrum going on. A character like that can work perfectly well as a main character in a book, but at least for me, you have to work twice as hard for it. Zoo City didn’t quite make it.
So it goes. It was interesting enough to read.