The Commentary introduces the books of the Bible in three ways. A set of general articles in the introduction deals with matters that concern the entire Bible. A second series of articles introduces the parts of the Bible that show a similarity and have a relationship to each other.
Then there are the commentaries on the individual books. This plan enables readers with three approaches for study: to the Bible as a whole, to the major divisions of its literature, and to the particular books.
James L. Mays, Harper's Bible Commentary