The final chapter of Joshua seems to focus on themes of God's agency, idolatry, and continuity. 

There is a strong emphasis on God's actions that have led the Israelites since Abraham - and especially since the Exodus. The history that has unfolded in Joshua is described as God's doing. Calls against idolatry are perhaps an expected theme as Joshua nears the end of his life, since this issue has been one focus of his leadership through the conquest of idolatrous nations. It is fascinating to reflect on the idea of continuity as we continue to learn from the story thousands of years after it was first written down.