King Rat by China Miéville

Saul wakes up one morning to find his father dead, and himself being framed for the crime which he did not commit. Stuck in prison with no alibi, he has little choice but to go along with the strange man who breaks him out; the man known as King Rat. As Saul learns about the supernatural world he has been thrown into--and his own past--he must decide whether to defy or accept his Rat heritage; and in doing so, find a way to save the world, and his friends.