Keith Mathison Ligonier Ministries has a list and discussion of his top five commentaries on Song of Solomon at the Ligonier Ministries blog. Mathison acknowledges that, “It is somewhat difficult to recommend a "Top 5" list on the Song of Songs because one's inclusion of commentaries in the list will largely depend on whether one takes an allegorical or non-allegorical approach to the book. The list below is based on my own non-allegorical approach to the book.” That being said, I would suggest that Duane Garrett (either or both his work in the NAC and WBC) is a better choice for the top two slots than either Gledhill or Carr. (Garrett takes a non-allegorical approach.) I would also add David Hubbard, Michael V. Fox (The Song of Songs and the Ancient Egyptian Love Songs), Tremper Longman (Cornerstone), and Jack Deere in The Bible Knowledge Commentary to the runners-up. In any case, the top five Mathison listed are:
1. Tom Gledhill -- The Message of the Song of Songs (The Bible Speaks Today, 1994).
2. Lloyd Carr -- The Song of Solomon (Tyndale Old Testament Commentaries, 1984).
3. Richard S. Hess -- Song of Songs (Baker Commentary on the Old Testament Wisdom and Psalms, 2005).
4. Tremper Longman -- Song of Songs (New International Commentary on the Old Testament, 2001).
5. Iain Provan -- Ecclesiastes, Song of Songs (NIV Application Commentary, 2001).