Ostensibly this is a book exploring the nature of a world that exists in a different geometry but underlying a number of social and psycological themes are explored.
The story follows the protagonist as he starts his apprentiship and is first introduced to the strange nature of the world he inhabits which has been hitherto kept secret from him. He lives on a city that must keep moving on tracks that are endlessly laid in front of the city (and taken from behind) in pursuit of an "optimum" point that never stops moving. Very little is ever explained to him, it is thought that they must find out for themselves and that no words could ever make them understand, such is the peculiar nature of their world and why the city must never stop.
The author does a good job of helping the reader visualise the weird topological shape of their world and the strange relativistic effects but I think that one's enjoyment of this book will be enhanced if one enjoys exploring such abstract concepts. If you enjoyed Flatland: A Romance of Many Dimensions as an excercise in helping to visualise a fourth spatial dimention then you should enjoy this. I was so caught up in my attempts to visualise what was going on that I missed my stop on the train!
But there's still a good story in here as well. This is not merely a flimsy story thrown together purely as a vehicle for exploring this concept. The characters aren't as fully developed as one might like but for me, that's not a big enough criticism to detract from my opinion that this is a science fiction masterpiece.
Note on the Binding: This is the first of the new bindings from the S.F. Masterworks that I have bought and I must say that I'm not impressed. There is a thin plastic coloured sheet affixed onto the plain white cover and mine has started peeling away from the most of the edges. Very poor quality indeed and I hope they are not all like this.