Red Shadows — Yvonne Navarro

It was the worst catastrophe the people of Earth had ever endured. In the summer of 2000, fragments of a rogue planet slammed into Earth. Billions were killed. The impact ravaged Earth, stopping its rotation. Now, twenty-one years later, the remnants of humanity face total extinction. They live a primitive existence in a land divided into perpetual daylight, eternal twilight, and endless night. From each of these worlds comes a threat that could destroy the fragile civilization that has survived....

A young man seeks his mother in the lawless terrors of the Darkzone, only to find horrors far worse than he could have imagined. A weary wanderer returns to a haven from his past, unwittingly leading a murderer to its unsuspecting people. And an impetuous explorer searches for treasures in a long-dead city, only to bring back an even more implacable killer: a plague called the Red Shadows...