Eternal Kiss of Darkness by Jeaniene Frost — book slip

Chicago private investigator Kira Graceling's life takes a dark turn when she stumbles upon a world of nightmares. Drawn by the sounds of pain, she finds herself rescuing Mencheres, a powerful Master Vampire, from a dire situation. Despite the danger, an undeniable attraction sparks between them. Mencheres, who has lived for centuries, is captivated by Kira's bravery and beauty. However, keeping her in his world could mean risking her life, while sending her away is unthinkable. As threats loom, Mencheres must decide between the woman he desires and the dark magic that could save them both.

For fans of Kim Harrison and Christine Feehan.