What books are missing from the Old Testament?

It depends on whose perspective you are looking at the Old Testament from.

The books missing from the KJV and the Hebrew Old Testament include Book of Jasher, Book of the Wars of the Lord, and Book of Songs. In addition, the Heather Bible has Acts of Solomon, Annals of King David and the Book of Samuel the Seer.

The Hebrew and Protestant Bibles also lack the Apocrypha, parts of which show up in different canons in the Catholic, Eastern Orthodox, Syriac, and Ethiopian. Each of those four canons has different sets of Apocryphal books and each has books lacking in all three of the others, especially in the Ethiopian canon.