Showing Butcher Bird by Richard Kadrey

Spyder Lee is a happy man who lives in San Francisco and owns a tattoo shop. One night an angry demon tries to bite his head off before he's saved by a stranger. The demon infected Spyder with something awful - the truth. He can suddenly see the world as it really is: full of angels and demons and monsters and monster-hunters. A world full of black magic and mysteries. These are the Dominions, parallel worlds full of wonder, beauty, and horror.

The Black Clerks, infinitely old and infinitely powerful beings whose job it is to keep the Dominions in balance, seem to have new interests and a whole new agenda. Dropped into the middle of a conflict between the Black Clerks and other forces he doesn't fully understand, Spyder finds himself looking for a magic book with the blind swordswoman who saved him. Their journey will take them from deserts to lush palaces, to underground caverns, to the heart of Hell itself.