Courting Midnight by Trinity Blake

Unjustly exiled to the mortal realm, celestial sex goddess Ava finds herself alone and powerless on the unforgiving streets of Las Vegas. Within minutes of her arrival, she is confronted by Duncan Pierce, a captivating, dark-haired dragon shifter, and is immediately drawn to the masterful guardian of the realm.
Duncan agrees to let Ava remain in the city as long as she stays out of trouble, but unfortunately for them both, hordes of demonic incubi are on the loose, terrorizing unsuspecting mortals and jeopardizing Ava’s freedom.
Ava and Duncan quickly find that there’s something much more sinister behind the invasion, and if they’re going to join forces to save the realm, they’ll have to deal with their growing attraction first.