Book Ezra the return of the Jews from captivity in Babylon and the rebuilding of the temple. Ezra is also responsible for leading then Jews back to proper behaving and worship of the God of Israel, though this is not really complete until the last chapter of Nehemiah.
Book Nehemiah primary mission was the rebuilding of the walls of Jerusalem. Secondary mission, social and religious reform.
Both Ezra and Nehemiah overcame obstacles after obstacles to finish the missions that God had given them. Because of their strong leadership skills, prayer, handwork, steadfast courage and even self-sacrificing examples, God saved the Jewish people from captivity in Babylon.