Esther is about God's sovereignty. God works so that a young Jewish woman becomes the queen of King Ahasuerus or Xerxes I. She becomes the queen five years before she is needed. The book describes a mortal conflict between Haman, the enemy of the Jews, and a jew called Mordecai. Esther saves the life of Mordecai and her Jewish people. You may be interested in visiting the Esther Q&A archive.