The Darkest King: William's Story – A Steamy Enemies to Lovers Paranormal Fantasy Romance (Lords of the Underworld, 15) by Gena Showalter

To become a king of the underworld at long last, William must resist an irresistible beauty—or a curse will ensure his end… A merciless prince feared by all… Cursed by a vengeful witch, William of the Dark will die if he ever falls in love—murdered by the woman who steals his heart. His lone shot at redemption is a book filled with indecipherable code. Break the code, break the curse. Now, centuries later, he’s condemned to a string of one-night stands…until he finds the only woman in the worlds able to set him free. A rare creature of myth and power… One of the last living unicorn shifters, Sunday “Sunny” Lane works from the shadows as a cryptanalyst, on the run from assassins and poachers. Then the darkly seductive William abducts her, holding her captive in Hell. The closer they get, the more she hungers for his touch…and the stronger a mystical desire to kill him becomes… But which desire will prove stronger—lust or death? And who will give in first? Read more