What is the structure of the Old Testament?

The Old Testament has 39 books, some short and some long, but can be broken down into 4 broad categories.

The 5 books of the LAW or the Pentateuch 

Genesis

Exodus

Leviticus

Numbers

Deuteronomy

It is not clear when the Pentateuch was written, but these five books contain the essentials laws/ codes, which define Israel’s history. The books contain stories of how the world was created, and how God called specific people to take Israel on a journey. It contains the Ten Commandments, and three key personalities are introduced, Abraham, Jacob and Moses. In the Jewish faith, these five books are called the Torah.