Inverted World is a cleverly-original – make that brilliantly unique – tale of post-apocalyptic survival, set on an inhospitable desert planet sometime in the future. A community of colonists from “Earth planet” now live in a mobile city (also called Earth) which must perpetually crawl northwards on a system of rails and winches, to escape the encroaching gravitational distortion in the south. Their world is a solid hyperbola: normal at the centre (or “optimum”, the point towards which the city is travelling) but horribly stretched to an infinite extent at either periphery. The city must keep moving because the ground itself is moving – forever threatening to draw them back, towards centrifugal destruction.

The city is sealed to all but the guildsmen, experts in their various fields (track maintenance, bridge-building, trade and so on) who secretly keep the city moving, ever-forwards; through the eyes of a young apprentice, Helward Mann, we see how the guild system operates. Helward has joined the Future guild, whose responsibilities include travelling “up future” (i.e. northwards) to study the lie of the land (and thus plan the city’s best course of movement), but also “down past” – southwards, towards the centrifugal distortion effect. Time passes at different rates in either direction, with serious consequences for the traveller: returning from a mission down past, Helward finds that what seemed to him to be a journey of several days has actually cost him two years. His new bride has since remarried, assuming he was dead – and with good cause, it turns out. Local unrest has been building against the city, with villagers taking to murdering apprentices who venture outside. The city, we learn, has a shortage of good breeding stock, and has been engaged in a highly-dubious bartering system – trading food for local women, in other words. The women (only the youngest and hottest, of course) enter the city, hook up with a guildsman, then are free to leave once they give birth; but any female babies must be left behind, to replenish the city’s gene pool. The village menfolk have taken exception to this, as many women prefer to stay in the city rather than scratch out a living in the wilderness; and before long, the city must defend itself against a series of fiery raids. But greater hazards lie ahead, which threaten to undermine everything Helward knows – or thinks he knows – about the world around him…

This is a fine book, with an ingenious premise and a strong sense of adventure. (It’s also very much a product of the early 70s, as Helward gets to enjoy himself with a trio of naked, compliant ladies at one point. Still, given his later trials, that seems only fair recompense.) The guild system is well thought-through, with Helward spending just enough time in each guild for us to appreciate the back-breaking slog involved in dragging an entire city across rocky terrain. The city itself is a marvellous creation, like a miniature Manhattan made of timber and steel, creaking along its rails towards an uncertain future; how it came to be here, on this topsy-turvy planet, nobody knows. The novel reaches its imaginative peak during Helward’s first visit down past, where he first sees the effects of the centrifugal drag: a mountain range flattened to the height of a few inches, human bodies grotesquely deformed, an entire world stretched and compacted to infinity. It’s a genuinely wild and alarming vision, and we share Helward’s panic as the world around him seems to go insane; and through him, we understand the vital necessity for the city to keep moving at all costs. The narrative switches from first- to third-person several times throughout, enabling us to experience Helward’s reaction to this unfamiliar world first-hand, while also establishing it in a broader context. Characterisation is spare, but effective; in an ideas-driven piece like this, you don’t want (or need) too much background baggage getting in the way. Inverted World is knockout stuff, clever and exciting, and a memorable addition to the ApocFic genre.