A very different creature from Miéville's uniformly excellent Bas-Lag books (Perdido Street Station, The Scar, Iron Council), The City & The City imagines a uniquely twinned pair of cities occupying an overlapping physical ('grosstopic') space whose inhabitants and governments are adept at 'unseeing' each other at every turn (all the while maintaining diplomatic relations with each other and the rest of the world, which is pointedly familiar and contemporary, marked by a stream of readily recognisably cultural references); the division is policed by a mysterious organisation called 'Breach', which swoops upon any egregious breachers in a matter of seconds, the unfortunate individuals never to be seen again.
The cities, Beszel and Ul Qoma, seethe with revolutionary groups and ethnic tension, plots and counter-plots, political and commercial intrigue and criminal activity; into all this is dropped a mysterious murder which appears to involve breach, investigated in classic (if, in many respects, necessarily thoroughly unconventional) police procedural style by the Beszel inspector Tyador Borlu. It's a vivid read, bulging with ideas and images of transgression, division and uneasy melding, of place, law, society, language - not as entertaining or compelling as the Bas-Lag series, but still impressively, muscularly intelligent and intriguing.