I found this, the last in my reading of the BSFA novel nominations, a fascinating read. Embassytown is an interface between humans and several different types of aliens; the human ambassadors who deal with them are identical twins, bred and conditioned to function as effectively a single personality with two bodies; this alone is a fantastic sfnal concept which has never quite been done like this. Lots of playing around with and about language, the meaning of humanity, and some sex as well; also we have the inevitable Miévillean revolution and subsequent battle against the forces of reaction (very weirdly and vividly conceived).
I'm sorry to say, therefore, that I actually didn't like it as much as The Islanders. I found the characters more baffling than engaging, and felt that while the setting was superbly realised, this was not as true of the story. My vote for Best Novel therefore goes to the many strands (in more than one sense) of Christopher Priest's The Islanders, followed by
Embassytown, Adam Roberts'
by Light Alone, Lavie Tidhar's
Osama and Kim Lakin-Smith's
Cyber Circus, in that order.