If you're simply here for a quicky answer to the question Do Literary Books Sell Fewer Copies than Genre Books?, the answer at first blush seems to be a messy "no." But Betteridge's law of headlines could have told you that. The question is why. Because we can answer the question so many ways: taxonomically, mathematically, philosophically, etc.
When you look closer, the answer isn't what you expect. Even if you expect the "no" because you know Betteridge's law. This is a far more complicated question than it seems at first blush, perhaps even unanswerable by the time we get to the end of this journey, which I argue is absolutely worth taking because of every issue and idea it touches. If we were comparing American car sales to subscription French equestrian lessons, we could probably make a pretty quick dollar-to-dollar comparison. But the moment you start saying something like "sales of fast cars," well I have to ask, does this include Geo Metros? Not at first blush, until you look under the hood and see the Geo Metro Turbo out classing a souped up Honda Civic on the racetrack.
So it gets messy.