What is a theme in the book The city of Ember

Also in the book The City of Ember one of the main themes is person vs person. This is a main theme because Lina is trying to find a way out while Mayor Cole only want to find a way out for him self. As her and Doon set aside their differences they find a way out before the Mayor does.

The central theme in The City of Ember concerns the need to act against oppression. Ember was established as a city of refuge to preserve the human species in the event of an atomic war or other apocalyptic event. But it was only designed by scientists to last about two hundred years.