This is an extremely well done post-apocolypse setting. By this point the population has built up where isolated groups of people are begining to expand beyond their borders. The books have a rich variety of political, economic, and religious systems, languages, art, technology. The story follows a natural progression as the society and people change as a result of the events of all the previous books.
Heros are explorers, inventors, diplomats, warriors as the needs of the environment change.