We start with a classic scifi set up of diasporic humans and FTL travel, although you have to give Miéville some credit for the FTL travel being a lot more unique and mystical than wormholes or whatever. A series of episodes in the narrator's life paint the aliens ("Hosts") for whom the town serves as an embassy to humanity in an increasingly bizarre light: A former ambassador can no longer speak to the aliens as a result of an unexplained tragedy, although he still understands them fine. Current ambassadors come in sets of twins and seem to have no individuality or humanity outside of that bond. The narrator, even as a small child, can understand most or all of what the aliens have to say in Language, but knows that they will never, under any circumstances, be able to understand her.

(I do think the intentional confusion over what the Hosts and Language are at a basic level for the first ~50 pages was part of the fun, so if you loved Blindsight etc. maybe don't read this review and just pick up the book)

Language has two notable features: it requires two voices at once, spoken in unison by a Host's two mouths, or else by human twins who have been raised from birth to have no individuality. And, Language, as far as we can tell, has no lying, no metaphor, and no representation. As the narrator remarks, it is barely a language at all, mostly just the conveying of one creature's perception to another.

The twists and plot obstacles that need to be solved are more or less perfect for the premise, in my opinion. This is very, very far from an airport bookstore fantasy where Elves Only Speak Truth, and all the questions about consciousness and language that immediately come to mind are central to the plot:

• Metaphors are too much like lying. How about similes? Well, they have to actually be witnessed to be referenced in Language. Our narrator "becomes part of Language" when the Hosts ask her to perform a bizarre but banal task so they can reference it as a simile (making her a minor celebrity).

• How about opinions and emotions? Are they "lies" because another mind can't verify them, or "truth" because they are self-evident to the speaker? If the hosts can only convey factual information, does it make sense to call them conscious or are they sort of just machines?

• There's an AI robot walking around that the hosts cannot understand, even when it speaks perfect Language, since it doesn't have a mind. But how can the hosts detect that? Is "detecting a mind" subjective with regards to a species or individual? If you had people read a script, with perfect pronunciation etc., but no idea what they are saying (Chinese-room style) could the Hosts understand?

• Language is not a binary ability. What happens when you speak just a little, or speak with an accent?

• What do the Hosts think of lies, if they are able to conceive of them at all? (I love the answer to this one: they have an entire festival dedicated to trying as hard as you can to lie, as a sort of public-speaking-sport.) And of course the broader question of how such a society (if we can call it that) will be react to humans and our duplicitous ways takes up most the book.

Most of these questions (but not TOO many of them!) are answered thoughtfully. Highly recommend if you kind of like the idea of hard sci-fi but also don't want crappy prose and physics shoved where it doesn't belong.

There were definitely a few parts where Miéville's otherwise admirable commitment to the bit leads things astray--at one point when the narrator is musing on Language we get this line:

FOR HOSTS, speech was thought. It was as nonsensical to them that a speaker could say, could claim, something it knew to be untrue as, to me, that I could believe something I knew to be untrue. 

Bro you gotta introspect a little we all do that constantly