Wayward Sky by Devon Monk

Brogan and Lula Gauge have spent a lifetime traveling Route 66, hunting the monsters that attacked them and left Brogan an earthbound spirit and Lula a near-vampire. They never wanted to catch the attention of Cupid, the god of connections and destruction. They never expected the god to want to strike a deal with them, either.
Cupid’s deal brought Brogan back to life, but now they owe the god a favor. They must find the spell book of the gods. A book of magic so powerful, it could destroy the world.
The hunt for the book leads them down the Mother Road, across Kansas and Oklahoma, and straight into the sights of a seer who is not a seer, a healer who is not a healer, and a man from their past who carries a deadly secret.
But for a chance to finally have the life together they want, a life they were cheated out of years ago, Brogan and Lula will fight any monster, face any magic, and take on any foe.

Even if that foe is Death himself….