The Island of Dr. Moreau is an oddball in dystopian literature. You see, most dystopian novels take place in the distant, dank, and dark future.
Take Orwell's 1984. It was first published in 1949, so the year 1984 was still a ways away. Orwell's novel tells of a world where an oppressive dictatorship uses rules and order to steal the rights of the public without them even knowing or caring. Orwell's goal is to craft a fictional future to warn his readers that this could happen one day—of course, had Orwell known the actual year 1984 would have brought us leg warmers and boy bands, he might not have found Big Brother so scary.
Wells' dystopian novel tells of an oppressive society where rules and order are cleverly used to hide the fact that the island's populace are all animals, products of the harsh and painful realities of Moreau's nature. The kicker? The novel isn't a warning of a possible future. It takes place in the present—well, what would have been the present at any rate. It's saying that this horrible possibility isn't a possibility at all. It's already happening, right here, right now.
Wells is making fun of us. All of us. The Beast Folk represent a satirical version of humanity as a whole. Their laws both symbolize and scorn our laws, from religious tenets to social contracts. The Beast Folk's ideas of beauty—how many fingers on a hand—is meant to point the finger at how odd and inane our measures of attractiveness are.
The final punch line: just like the Beast Folk, we pretend to be civilized and separate from our natural impulses when in reality we are just animals. Like any joke, you're invited to laugh or shake your head and wonder, "who comes up with this stuff?"
Finally, The Island of Dr. Moreau manages an excellent blend of horror and science fiction. It uses science to explore human progress through experimentation, in this case vivisection. Then it uses horror elements to question whether or not said scientific advancement is a good thing. And the blend is seamless, with each balancing and supporting the other. Think of it as a delicious genre smoothie, the kind with the perfect ratio of bananas and oranges (strawberries optional).