Unicorn Battle Squad

Mutant unicorns. A palace with a thousand human legs. The most powerful army on the planet. A first world city on the verge of collapse.
In a city where teetering skyscrapers block out the sky, a city populated by lowly clerks, rumors have been circulating of a terror in the east. When Carl, the lowliest clerk on the negative twelfth floor, discovers that the city is indeed in grave danger, he sets out to warn the city's protectors: the Unicorn Riders.
Although Carl's missing father has left him a unicorn of his own, it is a small and sickly creature. Even worse, there is a crab claw growing from its side. But the Unicorn Riders need as much help as they can get, and soon every able rider sets out for the city's flooded perimeter in a steam-powered Spanish galleon.
An epic journey that spans desert and sea, through the bedchambers of a fearsome Eastern queen, and into the devastation of a conquered city, Unicorn Battle Squad is the story of a boy and his unicorn at the end of the world.