The Mating Fire by Bonnie Vanak

A geology student must rely upon a sexy, but cursed incubus when she discovers she has formidable powers, and evil demons will do anything to claim her magick.
In the shadow of a mysterious volcano’s fiery peaks, Harper Ashley’s world erupts into chaos when she discovers she’s more than just a human student of geology. Saved from a demonic threat by the enigmatic Jared Griffin, she’s thrust into a realm where magick pulses beneath the earth’s surface. As Jared, an incubus with a secret past, teaches her to harness her latent magick, a forbidden attraction ignites between them.
Jared, a powerful incubus living a lonely life in a remote castle in Peru, was cursed to turn into a beast no woman could ever love every midnight. If he doesn’t find his soulmate soon to break the curse, Xavier, the Crystal Wizard, will be forced to destroy him before Jared can become a force for evil.
As Harper and Jared delve deeper into the dangerous mysteries of their intertwined destinies, Harper must confront the truth of her ancestry and the dark forces that seek to consume her newfound abilities. Can they withstand the inferno of secrets and shadows threatening to consume them both and save Jared’s soul from eternal damnation?