The Bible can be looked at as God’s lesson plan for humanity. And just like all lesson plans it is designed so that it is progressive and begins with simple things then works its way up to the more complicated things.
Genesis through Deuteronomy somewhat compares to Primary education. In that it teaches you the essentials. Just as primary education teaches you the basics of learning to read and write, the Pentateuch teaches you the basics of who God is and how he should be worshiped.
Joshua through Song of Solomon somewhat compares to intermediate school. In that it teaches you how to take the essentials and apply them to serving God.
The remainder of the Old Testament Isaiah through Malachi somewhat compares to High School. In that it teaches you the background of what you have learned, and how to apply it in a general form.
And finally the New Testament somewhat compares to Higher education. In that it is a refinement of all let you have previously learned, that giving you the why, and wherefore, and how to apply what you have learned to your life.
Now that we have covered the basics let us take a look at the book of Leviticus and determine exactly what we are supposed to learn from that book. just as in first grade you learned ABC's and the numbers, after that you learned how to make words and finally how to make sentences.
Just as first grade taught us our ABC's and numbers so Genesis taught us the basics of who God is and his relationship to man. Leviticus thing is equal to the part where we learned him make sentences and how to use what we learned in first grade. Now that we have mastered who God is in the book of Genesis, we are taught in Leviticus how to worship God.
The book of Exodus in some ways reflects early childhood in that after a child is born he must learn how to walk and talk. So with the nation of Israel, God had taken them from slavery and was now teaching them how to survive in the world. But the nation of Israel had not learned to completely depend upon God, when as the spies returned from looking at the promised land, they were afraid of the people that are and did not fully put their faith in God to give them the promised land.
So now we get to the book of Leviticus the main thing in the book, which God is teaching Israel is that there is no forgive this of sin without blood sacrifice. In answer to your question, God was having Israel repeat part of what they should have learned in Genesis. Apparently the reason that God had them make some sort of atonement for each and everything given them by God was necessary to their understanding that God was in control of everything. And just as God had used animal sacrifice in Genesis to show Adam and Eve required death because of sin, so he used animal sacrifices to take the Israelites the same message. Just as the teacher in primary schools re-emphasize or place greater emphasis in assuring that we learn everything completely, so was God teaching Israel that every sin required a blood sacrifice. And just as any good teacher will take the time to repeat something as often as necessary so God was repeating the lessons that Adam and Eve did not seem to pass on about God using animal skins to cover their naked bodies, and those skins represented the sacrifice of life.
I hope this helps.
