The Broken Kingdoms by N.K. Jemisin

In the city of Shadow, beneath the World Tree, alleyways shimmer with magic and godlings live hidden among mortalkind. Oree Shoth, a blind artist, takes in a strange homeless man on an impulse. This act of kindness engulfs Oree in a nightmarish conspiracy. Someone, somehow, is murdering godlings, leaving their desecrated bodies all over the city. And Oree's guest is at the heart of it. . .