What is the theme in Swan Song by Robert McCammon?

The need for power, or discipline and control is another theme. It is telling that, as soon as the apocalypse happens, people are vying for power in the new, broken world. In many places there is order, but it is built on fear and distrust instead of humanity banding together after tragedy. People have the instinct to survive, but very quickly descend into dark questions of what survival should be in the new world, and whether or not it is actually worth it.