Embassytown - China Mieville

It takes a while to get going, but once it does it becomes a smart story about the meaning of language. In the distant future, on a remote planet, humans live side-by-side with The Hosts, a very alien race that has two mouths and no difference between language and thought.  Interaction is mediated by Ambassadors, highly trained, genetically created twins. A new kind of Ambassador is sent by the government, which turns The Hosts into drug addicts with his voice.

The ending comes rather quick, glossing over some action sequences to wrap it up in a reasonable amount of time. More of a philosophical dissertation than a novel, but worth the read for the imaginative level of detail.