Did the story just jump 7 years forward? That was disorienting.
Comparisons with The Stand are inevitable, of course, and I was thinking how differently people, in general, were behaving in the aftermath of the apocalypse, and that McCammon must have a much darker view of humanity's essential nature than King does. Then it occurred to me that there is an enormous difference that could account for it - resources. In The Stand, a virus wipes out most of the people, but leaves nature and natural resources intact, along with most of the man-made resources, so there are few humans, but an abundance of food, shelter, and fuel. McCammon's is a nuclear apocalypse, so there seem to be more people, but scarce life-sustaining resources in a hostile natural environment.
So, yeah, of course people are going to behave differently.