What makes a good Hap & Leonard story is the weird confluence of events that starts in one place and takes you to on a roller coaster ride to a conclusion so far from the beginning that you have to look back to see how you got there. It doesn't usually feel convoluted (Captains Outrageous notwithstanding), and it's usually pretty tight. Since most Hap & Leonard stories are novels, this is a fine thing.
A Hap & Leonard novella, though, is something a little different. It doesn't have the time nor the pacing to develop a series of events like that, and what you're left with is a shorter work which is basically just the setup that would occur in a novel. Here, Leonard gets into a bar brawl that takes him to helping one of the brawlers protect his younger brother from getting involved with a criminal group. It's a satisfying story with the usual wit and grit one would expect from Hap and Leonard, but it wasn't quite the same as experiencing a full novel.
Anything by Lansdale is worth reading, though, and even if Hyenas is just mediocre when compared to the rest of the series, it's still worth the hour it will take to read it. Plus, if you've never read anything by Lansdale, this would be a good start. It's sort of like getting a sampler at a bar before ordering the 22-oz. growler.