It's that time of year again, when I'm reading my way through the Hugo nominations in preparation for voting, and this is one of the books that is up for Best Novella even though I'm not completely convinced that it actually fits the bill as either SF or Fantasy. The most you can say about River of Teeth is that it's alternate history, of which more shortly, though it still hits more genre buttons than some things that have been nominated in recent years...
Anyway, onto the plot - the basic premise is that, back in the mid-1800's, there was a plan to import hippos to the US which understandably failed to come to anything. In River of Teeth, that plan went full steam ahead and there was also work done to dam up part of the Mississippi when some of those hippos escaped and went feral. In case you weren't aware, hippos are very aggressive and dangerous animals and definitely not something you want to be messing with, though here they also serve a major role as replacements for horses in a part of the world that is significantly swampy.
Anyway, our story starts with our protagonist getting commissioned to 'deal with' the feral hippos and to do so he comes up with an ambitious plan, involving the need to recruit himself a group of miscreants and blow stuff up. Naturally, since this is essentially a western, there's a suitably oily villain who is a) responsible for crushing our protagonists' dreams previously and b) has a devious scheme of his own. Hijinks ensue.
River of Teeth is entertaining enough, with well-drawn characters that made me keep turning the page, but I'm not sure it entertained me enough to either vote for it in the Hugos or continue to read further in this series (since there's at least one sequel, Taste of Marrow).