There is a specific syntax (order) of elements for Bible headings: 

Bible. OT/NT. (book). (verses)--(sub-divisions)

For example:
Books about Genesis:
Bible. O.T. Genesis

If you want to narrow your search to Commentaries (usually verse by verse expositions of the text), you can type:
Bible. O. T. Genesis -- Commentaries

Books about the Gospel of Mark:
Bible. N.T. Mark

Books that contain a more sustained argument about a book or portion of a book of the Bible are usually included under the sub-division, interpretation and criticism.  For example: 

Bible. N.T. Mark--Interpretation and criticism

Bible as literature

Subject heading are not always intuitive, so please ask a librarian if you have trouble finding the material you need in the online catalog.