The Tears of the Sun: A Novel of the Change (Emberverse Series, Book 8)

It's Change Year 25, a generation after high-energy technology died in a catastrophe most of the human race didn't survive. The children born after the Change are now starting to take center stage - and Whoever or Whatever was behind the Change itself may be taking a hand in their rivalries. An expedition has travelled to Nantucked across a strange and hostile continent to find some answers.