A few years ago, I stumbled upon a copy of Daniel Doriani's commentary on the book of James. I read that book from cover to cover and was amazed at how well it was written. I did not know then that this was part of the "Reformed Expository Commentary Series" and there were other books like the one on James.
Years later, picked up Dennis Johnson's commentary on Philippians and it was amazing. Westminster Bookstore has a sale going with this series which includes the latest commentary from Iain M. Duguid on The Song of Songs.
To understand more of what these commentaries are about, here is a short video:
This sale will be going on until June 14, so take advantage of it.
Click on this link to see what commentaries and specials are offered.