The dead streamed past her like water. Fingers raked across her clothes as they passed. Her hair flew up around her face. They came so rapidly she couldn’t even tell that they were people. They were a force, and she was a force, and Nyle could take them all. Without speaking, Cait continued to chant in her mind, “Come, come, come.” She wanted every dead person in Downtown, and Old Town, and the Pearl.

Grave Cold, by Shannon Knight, is a really difficult-to-classify novel, as it blends multiple genres into it, creating something quite unique; a mix between dystopian sci-fi and fantasy, with some touches of biopunk, all of this combined with an amazing pace growing steadily during all the plot. And making use of some themes that I haven't seen explored much in the genre.

Nyle is attracted to the District of Portland by the call of death; his long life might end if he doesn't solve the situation. But the electronic walls that keep mutants away are also blocking Nyle's kind outside, making them unable to enter and free the recent dead from their bodies.
Cait's dreams are plagued by death; she's just a beautician struggling with the rent and trying to dodge GM police. Returning from a field trip, she's convinced by Nyle to smuggle him into the city; and later, her life will be shaken once Nyle reveals to her she's not genetically modified, but a necromancer. 

In the District, the dead are being trapped and used as an energy source. Nyle, with the help of Cait, must try to stop this technology from spreading, condemning those who pass to never experience the final freedom; but they are risking their own one, confronting the powers that control the district.

All of the hospitals seemed normal until they reached a decrepit clinic in a neglected part of town. The brick was rotting, leaving the exterior pitted with disrepair. Judging by a rectangle of brighter red, the sign seemed to have fallen off the building. No modern security devices blocked the door.

Grave Cold is quite unique in many aspects, starting with the world it is situated. While there are several elements of science fiction (advanced technology, genetic modifications) and dystopic ones, they are blended with fantasy ones, such as the ravens and the whole necromancy thing. Cities have become aisled entities, independent from each other and sometimes in conflict with others; corporations have a great share of political power. And meanwhile, citizens like Cait are not exactly living in opulence, quite the opposite actually.
Ravens are nomads, traveling from place to place liberating the dead from their bodies; and as a sort of reward, they live for a long time. They bring freedom to those who die, but in Portland, that's being negated, using the trapped dead as an energy source, reflecting the theme of profits over the people.

Nyle and Cait are both complex characters, and both are developed during the story. Despite his longevity, Nyle is a lonely character, trying to stay away from the people (he only came to Portland due to the call), and as a result of it, he's not used to the social customs, needing Cait's guidance for it. He's certainly brave, and soon, a real friendship with Cait appears. 
Cait is quite similar in the loneliness aspect, as you could say she prefers the company of Fred, her cat, over people. She accepts a big risk by helping Nyle, but similarly, she does it because she feels it is the correct thing to do.

“What happened when your science went astray and your people began to die?” Nyle asked. “Did the strong protect the weak and innocent? Did clans stand together? No. It was every man for himself. Let the weak die. The god of weak things didn’t stand in and protect you, either. Your governments preach peace and order while they form dictatorships and destroy their neighbors. Nothing much has changed. Only man can make a stand.”

Grave Cold's plot is marvelously structured, going from a relatively small scale, and growing gradually, showing progressively its internal layers, like a matrioska. This is combined with excellent pacing, fast but adding slower scenes in the middle that helps you to take a breath and organize all your thoughts. 
Knight also shows her strength in provoking feelings in the reader, packing several emotional punches during the narration, really impactful due to how much you get attached to these characters.

I would strongly recommend more people to read Grave Cold, independently of which genres are your favourite ones. It is such a unique novel, exploring themes I didn't certainly expect to see in fiction; an absolute pleasure to read.