The City & the City is China Miéville's best novel since The Scar, and the tightest and most politically observant of his career. It also continues a trend begun in his previous book, the young adult adventure Un Lun Dun, of working comfortably within established genres (the Bas-Lag novels were exclusively the products of Planet China) while simultaneously taking those genres apart and rebuilding them via his own idioms. The City & the City is existential pulp fiction. It's a hard-boiled detective story set in a scrambled world. It's got murders, conspiracies, secrets, red herrings, action and suspense to burn. And it's all upholstered in big ideas — about nationalism, cultural identity, the fear of absolute authority, the perceived threat of borders and their violability, and the overpowering irrationality of xenophobia.

Miéville has always been fixated on cities. New Crobuzon and UnLondon are characters as vivid, if not moreso, as the diverse natives who amble their living streets. But to Miéville, cities are defined by their peoples, not so much their geographies. Cities can be anywhere, and they don't necessarily have to stay put. Indeed, both The Scar and Iron Council take place in vagabond cities that are entirely motile, founded by outcasts and undesirables who have evolved their own form of nomadic urbanity.

But while turf alone may not be especially important to Miéville, he understands full well how important it is to populations as a whole, and a people's sense of identity and place. The need to put down roots, to define this place as one's home, is etched into our very being. Nationalism is much on the minds of people who feel their borders are being challenged and threatened. Recent history is full of the agony and anger of division. Conflicts between England and Ireland, and between Catholics and Protestants in Northern Ireland, where individual neighborhoods must be walled off from each other; the splitting of Germany into East and West, lasting for decades before reunification; and that mother of all turf battles, Israel vs. Palestine, which, in my more cynical moments, I'm convinced will not end until the last living Israeli and the last living Palestinian kill each other. Even here in the smug USA, our porous border with Mexico, through which drugs and illegal immigrants flood as if through a broken dam, is a perennial political hot potato.

In The City & the City, Miéville ups the ante. Taking place in the present day, the story offers us two fictitious eastern European city-states, Beszel and Ul Qoma, that are fighting not merely over a shared border but literally the same little patch of reality. The cities exist atop one another, oddly overlapped and fused together, like two superimposed film images. Some time in the distant past, an event called the Cleavage somehow split this little slice of the planet into two planes. We don't know what happened there or how, and it isn't the goal of the story to explore the science of it.

Besz and Ul Qoman citizens must be the most neurotic people alive. By law, they must choose to ignore — to "unsee" — those parts of each other's cities that occasionally obtrude on their own. One can be "in" Beszel or Ul Qoma, but whichever of the two you inhabit, you must be wary of those "crosshatched" areas of the city where bits of the other city are more visible than otherwise. A person in Beszel can be walking the sidewalk right next to someone in Ul Qoma. They are side by side, but a whole city, and a whole reality away.

Violations of this bizarre boundary are considered Breach, and harshly punished by a mysterious Orwellian law enforcement body who somehow exist independently and above both cities, who possess frighteningly omniscient surveillance powers and apparently limitless punitive ones. (Being marched away by man-in-black types you didn't know existed, who materialize out of nowhere and know everything about you is a distinctly European horror.) But this doesn't stop both cities from developing the expected rebel countercultures. Left wing unificationists, who favor the assimilation of both cities, duke it out with right-wing nationalists. Perhaps the fact they keep each other busy and are already well policed by each city's own law enforcement bodies is why the fearsome Breach mostly leave them alone. All the same, it's hard to understand why Breach is so punitive, what exactly would be so drastically damaged by more of an open-border policy here. This isn't a plot flaw; quite the opposite. Miéville's making a point about nationalism raised to the point where simple xenophobic fanaticism is enshrined as policy. Unlike the Irish Catholics and Protestants, or the Israelis and Palestinians, there's no deep-seated religious or political or cultural divide that separates the Besz and Ul Qomans through implacable prejudice and hate. The citizens of either city don't really seem to have a problem with one another. They maintain their strict separation because laws demand it, laws only a few bother to question.

I don't see how either city can possibly be a happy place to live, but the locals seem to manage. Ignoring crosshatching gets to be just another exercise in willful blindness, like stepping over homeless people on the sidewalk. And besides, Ul Qoma and Beszel do interact, and there is a legal way to travel from one to the other, through a tunnel beneath the central government building with the bizarrely suggestive name of Copula Hall. Both cities also interact with the outside world, to varying degrees. The US has blockades against Beszel for some reason, but trades freely with Ul Qoma, with the result that Ul Qoma is quite a bit more modern than Beszel. Western Europe is somewhat more charitable towards Beszel.

Though it contains none of the baffling creatures and none of (or very little of) the steampunk trappings of his Bas-Lag novels, The City & the City offers us a world no less vivid, and even more disarming for its clear analogies to so much political reality. The plot itself is a deliciously convoluted police procedural, a kind of CSI: Miéville, in which a simple murder mushrooms into a potential international catastrophe. When a Canadian student working an archaeological dig in Ul Qoma turns up dead in Beszel, Besz detective Tyador Borlú, working together with Ul Qoman investigator Qussim Dhatt, uncover what looks like the proverbial conspiracy with leads going Straight To The Top. The killing was committed in such a way as to assiduously avoid committing Breach. As the list of suspects comes together and the stakes become clearer, it appears the victim learned something she shouldn't, something that could threaten the precarious existence of both cities.

This is unabashed pulp stuff, and wonderfully entertaining. It's the closest Miéville has come to offering us pure popcorn reading (well, next to Un Lun Dun, but that was marketed as YA, after all). At just over 300 pages, it's his shortest book, but also his most efficiently constructed and fast paced. And the sociopolitical themes explored in its subtext just make The City & the City doubly rewarding. Would it be better for one or the other of these cities to fall, or for them both to unite? Or for them to continue business as usual, two entire populations living elaborately constructed lies for the sake of...what? Patriotism? Cultural autonomy and pride? Easy answers here? Not a one. No wonder so many people find it easier simply to do as they're told.