The books of the Old Testament can be grouped into 4 categories: torah (the first 5 books), history, prophecy, and writings. The writings are further subdivided into psalms and ‘wisdom’.
The wisdom books are:
Job – 25 pages
Proverbs – 21 pages
Ecclesiastes – 6 pages
Song of Solomon – 5 pages
Wisdom (of Solomon) – 16 pages
Sirach – 41 pages
(page counts from the Revised Standard Version)
The latter two are not in abridged Bibles, for which the ‘wisdom’ category is 57 pages instead of 114 pages, ie half the size.
Abridged Bibles are also missing some historical books (Maccabees); however, it is the hiding of the wisdom books which most distorts the scriptural background to the New Testament.