Leviticus is the third book of the Old Testament. It follows Genesis and Exodus. Unlike those two, Leviticus is not presented in a story format. There are no primary characters like Adam and Eve, Cain and Abel and Abraham, Isaac and Jacob in Genesis or Moses, Aaron, Miriam and Pharaoh in Exodus. By comparison, Leviticus outlines a series of laws proscribing how people should live. The book of Leviticus essentially lays out a foundation for how people should behave and treat one another. It is the underlying architecture that enables the Israelite people to live together as a community.
The laws presented in Leviticus range from how to eat, dress, work, live, even how to rest. For instance, it talks about reaping the fields during the harvest so that the corners of the field are untouched, thereby allowing the poor to reap the produce and fruit themselves for their own use. Leviticus also talks about how to dress and even what fabrics are allowed and which are prohibited. It discusses what to eat and how to give thanks for what we have to eat.
The religious basis for this becomes apparent in the prior book of the Old Testament, Exodus, in particular in the chapter of Jethro. In Jethro, Moses ascends to the top of Mount Sinai at Yahweh’s command, while the Israelite people remain below and wait. Yahweh assures Moses that there will be a dense cloud that will accompany the people so that they can trust him that Yahweh’s presence is nearby.
Once Moses descends from Mount Sinai, he presents the Ten Commandments that Yahweh imparted to him at Sinai. In addition to these core commandments, there are 603 additional commandments presented. It is therefore logical that Leviticus follows Exodus because the commandments are given in Exodus and explained in detail in Leviticus.