Ligonier Ministries has a list and discussion of their top five commentaries on Esther. I would replace Baldwin with Berlin. I would also add M. V. Fox (Character and Ideology), C. M. Bechtel (Int), F. B. Huey (EBC) to the runners-up list. In any case, the top five Keith Mathison has listed are:
1. Karen Jobes -- Esther (NIV Application Commentary, 1999).
2. Joyce Baldwin -- Esther (Tyndale Old Testament Commentaries, 1984).
3. Iain Duguid. -- Esther and Ruth (Reformed Expository Commentary, 2005).
4. Frederic Bush -- Ruth/Esther (Word Biblical Commentary, 1996).
5. Mervin Breneman -- Ezra, Nehemiah, Esther (New American Commentary, 1993).