Dark Immortal, by J.K. Coi, is the powerful story of the love affair between Diana Latimer and Alric. She is a mortal engineer who rescued the immortal Alric when she found him in chains, underground, near an area she was excavating as part of her work. She nursed him to health, they fell in love, and they married. In this book, they face a severe dual crisis. The crisis requires that Diana and Alric heal a rift in their relationship that occurred in conjunction with a demon attack on Diana so that they can play their roles in a larger cosmic crisis to fight the demons. 

Coi creates a supernatural realm peopled by immortals and demons who have superhuman abilities but human feelings and desires. It's inhabitants mix freely with the human world. They can marry human woman and father children.  In Coi's world, Mastema and Karnage, the strongest of the demons, vie for power. Each has at "his" disposal demons, most particularly Rage demons. In Dark Immortal, the Rage Demons are freed and attack the women the Immortals have married. Why this is so and how Diana and Alric combine compassion, courage, human feelings, and supernatural abilities to fight these demons unfolds as the plot develops.

Coi's universe is complex and elegant. It is well-structured with no loose ends. The plot is complicated, as is the backstory of Diana and Alric, but it unfolds seamlessly. Because Koi stays on the feeling level, the reader might not realize how complicated the nuances of her story are, particularly the backstory of Diana and Alric. Dark Immortal is a beautifully written book. Koi uses its length to explore her characters in depth and reveal their pain, courage, love, hope, fear, and strengths. The book begins with Diana recovering from a demon attack that has taken her memory. Her memory, the flashbacks of her marriage, and the increasingly complicated plot unfold smoothly while the reader stays with the characters. Coi's protagonists are easy to identify with because they have classic virtues and faults, deep feelings, and moral qualities. Their moral qualities inform both their love and their heroic actions.

Diana and Alric are strong equals when it comes to virtues. Their relationship is that of a passionate woman and an alpha male who need, respect, and depend on each other. It is very hard to write like this and I have not seen many writers do what Coi can. She is great at emotions and great at lengthy sex scenes. I would read another J.K. Coi book in a minute!