Since we just started the book of Leviticus in our Bible reading schedule, I wanted to post some extra info taken from the "All Scripture Is Inspired" book (pgs 25 & 26) that helps to have in the back of your mind while you're reading Leviticus.
"...the book consists chiefly of the regulations of the Levitical priesthood, which was the chosen tribe of Levi, and the laws that the priests taught the people: "For the lips of a priest are the ones that should keep knowledge, and the law is what people should seek from his mouth." (Malachi 2:7)
Why was Leviticus written?
"As a new nation journeying toward a new land, Israel needed proper direction. It was still less than a year from the Exodus, and the living standards of Egypt as well as its religious practices were fresh in mind. Marriage of brother and sister was practiced in Egypt. False worship was carried on in honor of many gods, some of them animal gods. Now this large congregation was on its way to Canaan, where life and religious practices were even more degrading. But look again at the encampment of Israel. Swelling the congregation were many who were pure or part Egyptian, a mixed multitude who were living right in among the Israelites and who had been born of Egyptian parents and were raised and schooled in the ways, religion, and patriotism of the Egyptians. Many of these had undoubtedly indulged in detestable practices in their homeland only a short time before. How neccessary that they now receive detailed guidance from Jehovah!"
(Based on the fact that the Canaanites had some seriously gross and immoral practices such as pedophilia, incest, and bestiality, among other things, you can really see why the Israelites would need to be given such forceful, clear-cut regulations...so that those 'new laws' regarding clean moral conduct, would be firmly implanted in their minds & hearts PRIOR to entering the land of Canaan.)
"Jehovah had purposed to have a holy nation, a sanctified people, set apart for his service. From the time of Abel, faithful men of God had been offering sacrifices to Jehovah, but first with the nation of Israel did Jehovah give explicit instructions regarding sin offerings and other sacrifices. These, as explained in detail in Leviticus, made the Israelites aware of the exceeding sinfulness of sin ... these regulations, as part of the Law, served as a tutor leading the Jews to Christ, showing them the need for a Savior and at the same time serving to keep them as a people separate from the rest of the world. Especially did God's laws regarding ceremonial cleanness serve the latter purpose." but also, "Its statutes regarding diet, disease, quarantine, and treatment of dead bodies reveal a knowledge of facts not appreciated by worldly men of medicine until thousands of years later. God's laws regarding animals unclean for eating would protect the Israelites while they traveled. It would safeguard them against trichinosis from pigs, typhoid and paratyphoid from certain types of fish, and infection from animals found already dead. These practical laws were to direct their religion and their lives that they might remain a holy nation and reach and inhabit the Promised Land. History shows that the regulations provided by Jehovah gave the Jews a definite advantage over other peoples in the matter of health."