When the Old Testament canon was being formed there was a debate over whether or not Esther should be included. The main reason some questioned the divine authorship of this book was because there is no explicit mention of God anywhere in the story. The very thing that caused some to question the authenticity of this book is actually its contribution to Old Testament theology.
Esther is a wonderful reminder that God is present even in his absence. There are so many times when it looks and feels like God is simply nowhere to be found. In the historical context of Esther this was definitely the case. But as you read the book of Esther the invisible hand of God is unmistakable. God is preserving and rescuing his people unbeknown to them. God is often at work in this way—the way that we do not see and do not acknowledge. We need the reminder that God is present in his absence.