What is "railsea"

Railsea is a young-adult novel written and illustrated by English writer China Miéville, and published in May 2012. Miéville described the novel as " weird fiction", io9 labeled its mix of fantasy and steampunk elements as "salvagepunk" and the story has been seen as an "affectionate parody" of Herman Melville's classic novel Moby-Dick, also drawing on Robert Louis Stevenson's adventure novels Treasure Island and Kidnapped.