Inverted World is a science-fiction work of Christopher Priest, first published in 1974. The story sets place in a future world where Earth has been changed by some gravitational phenomenon so that humankind can only live near a specific point on Earth called the "optimum." As this "optimum" moves all the time, in order to survive, the guildsmen, the people who are entrusted with the safety of the people and secret of this world, are constantly building tracks and winch their city over them, constantly chasing the "optimum". Helward Mann is one of the guildsmen of the city and through his training to become a full guildsman, he slowly discovers the secret of the world that he lives in.

This book was one of the most refreshing and creative sci-fis I've read in a while. The writer managed to set up such a bizarre world logic and naturally illustrate the terrifying yet logical implications and what-ifs of living in such conditions.

The protagonist, Helward, also has a well-written storyline. You can experience the physical and emotional turmoils he's taken from the moment he took an oath as a guildsman until he is finally faced with the true truth of his world. The book's setting is amazing in itself, however, it would not be the same without Helward's dutiful yet somehow sad story.

And I love the ending as well. It's the kind of ending that ties up all loose ends without making you feel like you've been cheated by the author. It's all explained thoroughly in the end, and you're reminded of some things that still don't add up. The things that keep your mind in this world long after you put the book back on the shelves. 

Overall, a 100% must-read for sci-fi readers. What a remarkable story.