Here is the book’s description from the Amazon website:
DOING RIGHT ISN’T EASY IN A WORLD GONE SO WRONG
Cass Dollar outlasted the fall of civilization. But surviving Aftertime requires the kind of toughness that can conquer the violent landscape of California and still retain its humanity.
When a young boy and his dying grandmother are brought to the Box, the survivalist community where Cass takes shelter, she realizes that without her help he won’t be long for this unforgiving new world. But while the Box is a haven from the roaming marauders—and the flesh-hungry Beaters—it forbids children within its confines. The boy will be turned out to fend for himself. All that stands between him and the brutal wilderness is Cass’s protective instincts, and the stubborn resolve that’s gotten her this far Aftertime.