Magic Strikes by Ilona Andrews

Drafted into working for the Order of Merciful Aid, mercenary Kate Daniels has more paranormal problems than she knows what to do with these days. And in Atlanta, where magic comes and goes like the tide, that’s saying a lot.

But when Kate’s werewolf friend Derek is discovered nearly dead, she must confront her greatest challenge yet. As her investigation leads her to the Midnight Games—an invitation only, no holds barred, ultimate preternatural fighting tournament—she and Curran, the Lord of the Beasts, uncover a dark plot that may forever alter the face of Atlanta’s shapeshifting community…