Feral by James Demonaco and B. K. Evenson, 309 pages

Allie Hilts was in high school the day the world ended. It started when a fire at a top secret research facility released an airborne pathogen that infected every male, killing most of them. The few men who survived were changed, becoming stronger. They were unbelievably aggressive and violent. No male was spared, and no woman was safe. Allie and her sister, Kim, witnessed every man they loved be consumed and do the unthinkable. They were the lucky ones.
Three years later, Allie and Kim have joined a group of survivors in an isolated, walled-in encampment, trying to find a way forward in the new world. Outside the guarded walls the ferals roam-new monsters the women used to know as fathers, brothers, sons, and lovers. Now, Allie has been noticing troubling new patterns in the ferals' movements and a disturbing number of new faces in the wild. Something catastrophic is brewing on the horizon, and time is running out. The ferals are coming and there is no stopping them.

A fantastic new read. Very dark and creepy.