Shadow — David L. Dawson

Magic and shadow clash.
Enemies become friends.
Friends become enemies.

Cressida has been bonded to the Book of Fire. Assassins and shadow gods want the book and the only way to get it is to kill her. So Cressida has no choice but to ask for the help of her mortal enemy, Emily Swine. Meanwhile, Abe the assassin is starting to have second thoughts about killing Cressida, and Joe has been possessed by an irie who also wants the book. Prepare for a reckoning...