The story is about Sham Al Soorap a young apprentice on a train which hunts Moles.
Its the future, the sky is poisoned. So is a lot of the land. The only way to travel is over the sea of rails crisscrossing each other. The rails themselves have been built before and No one knows how they came to be. Myths and deities abound.
On the railsea there are moles, not your ordinary moles but giant ones who are hunted. A lot of captains have particular targets referred to as philosophies. Sham is on a doctor's apprentice on Medes, one of those trains.
The Railsea itself is described beautifully in sparse prose with well chosen words.
The book has a lot of substance. It doesn't have any romance that stifles the storytelling as in most novels. The moles themselves are beautifully done. Mieville excels in describing the hunt, putting you in the scene and his omniscient narrator is a delight. Parallels with Moby Dick are ever present but the story is much more deftly told.
Also present are tropes from the world of marine adventures. The pirates, the navy, captains with personal ticks and its amazing how everything fits together.
All in all its a great story and one of the better reads of the year.
China Mieville is inventive as usual. Its a great book but for some reason I didn't enjoy this as much as the rest of his ouvre. High expectations tend to that though and I had tremendous ones from Railsea.