The book of Leviticus shows the following: 

1) Man's great need for sacrifice and

2) God's provision for the priesthood reveals the need for a mediator.

Basic Outline for the Book of Leviticus:

Chapters 1-7: God's outline for sacrifices and burnt offerings (5 sacrifices:  burnt, grain, peace, sin & trespass)

Chapters 8-10: Details regarding the priesthood

Chapters 11-22: Dietary laws, uncleanness and behavior codes

Chapters 23-24: Feasts and festivals

Chapters 26-27: Conclusions and reminders