The first five Old Testament books are known as the Books of the Law, or the Pentateuch or the Torah.
Genesis, Exodus, Leviticus, Numbers and Deuteronomy
The first 11 chapters of Genesis tell about God. Through the stories of Creation, The Great Flood and The Tower of Babel we see that God created everything, and He loves and actively sustains all His creation. The remainder of Genesis tells the history of the patriarchs. The Jews trace their ancestry to a man named Abraham through his son Isaac and grandson Jacob. The Muslim Arabs also trace their ancestry to Abraham, through his son Ishmael. Exodus and Numbers tell the story of Moses, who led the Hebrews out of captivity in Egypt around 1300 B.C. They wandered for forty years in the desert before arriving at their Promised Land. During the time in the desert, God gave the Ten Commandments to Moses. Leviticus and Deuteronomy discuss the relationship between God and His chosen people, the Hebrews. They also give details of the Law that regulated almost every aspect of Hebrew life. Moses is considered to be the author of the Pentateuch.
(Note: Description used with permission from www.gotquestions.org)