Sins of the Night by Sherrilyn Kenyon

All the Dark-Hunters must follow a code of conduct- they must hunt Daimonites, protect humans from Daimonite attacks, Drink no Blood, Harm no Humans and Never Fall in Love. But there are always Dark-Hunters who break the rules, who become convinced that Acheron, the first and leader of the Dark-Hunters is something monstrous who is using them in a war of his own.

But punishing those who transgress the rules is too painful for Acheron, and could unleash the very destructive powers he keeps locked away inside him. Letting loose his rage could destroy the world. So Acheron leaves that to his Alexion- a man who was the second Dark-Hunter created- the one who was imperfect, before Acheron had the true secret of how to bring human warriors back correctly. Alexion lives with Acheron and Simi, Acheron's personal demon- a young demon who is little more than a child, in a place called Katoteros. He's only allowed to go to earth when a rebellion against Acheron is brewing in the ranks of the Dark-Hunters. And now, once again, it is time.

Alexion is sent to Earth to meet with Dangereuse St. Richard- the one Dark Hunter who Acheron likes and wants to save, and to investigate the Dark-Hunter who is causing the rebellion, a Dark-Hunter named Kyros whom Alexion knew back when he was alive and named Ias. With only two weeks to investigate the claims Kyros is making and possibly find a way to save his mortal former friend, as well as the rest of the Dark-Hunters who Kyros is trying to sway from Acheron's side.

And while Alexion is human for two weeks, he wants to find a woman to let out all of his pent-up lust on. Normally, he'd be bunking with a male Dark-Hunter and find a woman he could just make love to and leave, but Alexion finds himself attracted to his host- Dangereuse, now called simply Danger. And a Danger she proves to be to Alexion's heart. Killed by her husband during the French Revolution when she tried to save the noble members of her own family, Danger has never known a man like Alexion, or cared as much for one.

And even though she knows that Alexion is there to investigate and pass judgement on her fellow Dark-Hunters, she cannot keep from being fascinated by hum, or from falling for him. But when her own fellow hunters, and a Daimon called Stryker, are allied against her, can she survive the coming confrontation and keep Alexios alive? or is that to much even to ask from Danger?

This is nominally a Dark-Hunter novel, but allows us to see how rogue Dark-Hunters are policed. Since Ash can't do it himself, we are shown his judge, jury and executioner- Alexion. And while Alexion isn't exactly perfect for this job, he's biased and wants to save Kyrios, he's the only one who can do it for Ash.

Alexion hasn't been human in thousands of years- he can't taste food and is mostly spirit while in Katoteros, but he still is a man and feels lust and sexual feelings. Only his heart has never been engaged- until Danger. As he comes to care for her as more than just a woman to assuage his lust- and that starts pretty much right away, he wants his liason with her to last for more than just the few puny weeks he's allowed to be on earth. But how can that be possible? Will he once again find love, only to lose it?

The ending to the story tore my heart and made me cry, and it will certainly make you feel the same emotions when you read it. The last few scenes just about killed me to read, and yet I found myself loving the entire book. I love the entire series, but this one is close to the top as my favorite, and I sincerely recommend it to anyone who enjoys love stories, paranormal romance or urban fantasy romance. With a wonderful, enthralling backstory and amazing world, you'll find yourself coming back to this series again and again. Highly recommended.