It is a compact commentary, goes quickly through each book treated, usually brief explanation on a single verse (or two) or part of a verse, and one or two relevant quotes from Reformed authors. Nothing linguistic or minute (unless highlly relevant to that brief explanation) and then not very complicated. The whole commentary is only a few hundred pages. but there is a lot of good there, especially in the choice quotes.
I have found it very useful. I have it in parts, all except for the volume on Colossians/Philemon (which was out of print when I bought them).