Dark Union - The Descent Series, #3

Every fifty years, the most powerful ethereal and infernal beings convene on Earth to resolve conflicts with mediation by kopides--humans born to police relations between Heaven and Hell. They're meeting in Elise Kavanagh's territory this year, and she used to be the greatest kopis in the world. But she's not invited. An old friend, Lucas McIntyre, asks her to attend the summit in his place. But when she arrives, she discovers that a human faction called The Union has taken charge of the summit, and they're not playing nice.
Worse yet, someone has killed a prominent Union member, and now they're demanding blood. Elise has to bring justice to the summit in DARK UNION, an urban fantasy novella featuring a decrepit ghost town, angry men with guns, and even angrier angels.