Best. Premise. Ever.
First, go listen to this segment on This American Life: "Hungry Hungry People." (Or you can read the Kindle Single on the same story.) It's the true story of how, in the early part of the 20th century, Congress considered solving a food shortage by populating the Louisiana bayou with hippopotamuses.
In her novella River of Teeth, Sarah Gailey takes that proposal, pushes it back 50 years, and imagines the cowboys who would herd and manage hippo production. This is an amazing alternate history premise.
It's put to the service of what is essentially a heist story, in which five sketchy folks team up to pull off an elaborate plan that will make them a big pile of money--clear this big stretch of water of all the feral hippos. (Also, one of the characters is out for revenge.)
Verdict: more heist than the book could handle; not nearly enough worldbuilding.
I am really hesitant about "I wanted more" as a criticism of a book, because the best books are able to create realism without drilling down into all the detail, and evoking a fully realized reality is often enough. But I wanted more here because reality did not feel as concrete or specific as I wanted it to be. It's not that I needed more heist, or more backstory, or more time with the characters. I needed a deeper understanding of what was going on.
One issue was that there were just too many characters for a novella. Five folks on the job, the villain, and the lawman. If the five on the heist had been an established team who fit together neatly, that might have worked out, but the amount of infighting and double crossing and getting to know each other was just overwhelming, and I felt like I got only a loose sketch of most of the characters. They were all very different, but I still had some trouble keeping track (the two main female characters both had names that started with A, which confused me more than it should have).
I'm a bit skeptical about the hippo lore, too. I assume the author did plenty of research, and I know that hippos are violent and dangerous, but they are not generally meat eaters unless driven to it, so the "hungry" element of the danger of the ferals seemed out of place to me. If it had been explained why they were so eager to eat people, maybe it would have felt more real?
Also, we didn't find out what the heist was about for the first half of the book. There's the actual, legit job, the trick they have to make it worth their time and money (but if that was the plan, why did they need a con artist?), and the secondary goals of all the main characters. It was too much and it never really came together for me.
Which is a shame. Because hippo cowboys, y'all. Hippo. Cowboys.