Embassytown is an intelligent, if disembodied and sweeping, exploration of human-alien contact and of language in general. In an interview, Mieville said hat he felt this was his first actual science fiction novel in that it relies on so many of the tropes of science fiction—aliens, spaceships, AI, bio-mechanics, etc. The book uses them well without making them seem trite or overused and does so without resorting to the fairly standard human-alien relations plot (the one where one side is single-mindedly trying to exploit or kill the other) and I am always a fan of avoiding such overly-simplistic encounter stories. Readers unaccustomed to his style, however, might feel a lack of investment in certain scenes and characters (as I did) due to his narrative technique, which favors sweeping exposition over scene-driven plot development. Still, the book it hangs together overall, even if it does tell more than it shows.
In essence, I would describe Embassytown as a book that attempts to flesh out a complex and novel human-alien encounter scenario by using solid linguistic ideas to facilitate intelligent play with and language and perception. It can defininitely act as a primer for us to think about how we rely on language, since the Hosts attempt to harness simile and metaphor is a pretty concrete example of exactly how we humans employ figures of speech to tackle complex and abstract ideas. But Embassytown presents it in such a way that the aliens feel truly alien, which makes it a unique experience that will keep you thinking about it even after you put it down. There seem to be very few SF books that take the language barrier as its core speculative concept; Samuel R. Delany's Babel 17 comes to mind, but little else, so this is yet another way in which Embassytown made for a very novel reading experience.