What follows is a brief literary outline of the Book of Leviticus as I understand it:
A. Sacrifices/Offerings (ch.1-7)
B. Priestly Ordination (ch.8-10)
C. Clean/Unclean in daily life (ch.11-15)
D. Day of Atonement (ch.16) 
C’. Holiness in daily life (ch.17-20)
B’. Holy Orders (ch.21-22)
A’. Holy Observances (ch.23-25)
Conclusion: Blessings-Curses and Dedication (ch.26-27) 
I think the book offers a chiastic literary structure that demonstrates a literary unity overall and that places the Day of Atonement at the center. Many refer to this book as being about “holiness” (which it is), but holiness toward what end?
Toward the blessing of Yahweh’s presence with His people. As I stated in my earlier post, I believe that the intimate presence of Yahweh in relationship with His people is the point of Leviticus. Holiness is the means by which this is accomplished, but the aim is nearness in relationship. This is further clarified by the last two chapters which delineate the associated blessings-curses with faithfulness to Yahweh and the voluntary dedication of persons and properties to Yahweh. While all that precedes is commanded of Israel in their relationship with Yahweh, the final chapter speaks to what is voluntary in that relationship. The promised blessing in that relations was: “I will put my dwelling place among you, and I will not abhor you. I will walk among you and be your God, and you will be my people.”(Lev. 26:11-12 NIV)
 Leviticus 16 as the literary “center” of the book is also argued by Joel N. Lohr, “The Book of Leviticus” in A Theological Introduction to the Pentateuch: Interpreting the Torah as Christian Scripture (Eds., Richard S. Briggs and Joel N. Lohr; Grand Rapids, MI: Baker Academic, 2012), 87; and cited in that volume is the work of Wilfried Warning, Literary Artistry in Leviticus, Biblical Interpretation Series 35 (Leiden: Brill, 1999), 178.
 Admittedly, many scholars consider chapter 27 to be a sort of appendix. I have included it as part of the conclusion because of its voluntary nature for a people who have already covenanted relationship with their God, Yahweh.
 For several alternate and more complex chiastic proposals that do not describe the whole book, see Nobuyoshi Kiuchi, “Leviticus, Book of” in Dictionary of the Old Testament: Pentateuch (Eds., T. Desmond Alexander and David W. Baker; Downers Grove, IL: InterVarsity Press, 2003), 524.
 Critical scholars even go so far as to refer to chapters 17-26 as a so-called “Holiness Code” which was codified at some other time than the book it has been included in and only later attached because of the emphasis throughout the whole work on “holiness.” One of the commentaries I am using is notably called “Holiness to the LORD: A Guide to the Exposition of the Book of Leviticus” by Allen P. Ross (Grand Rapids, MI: Baker Academic 2002). It is because “holiness” is considered the watchword of this book of Scripture (which certainly seems pertinent), but I believe my point remains: holiness to what end?
Such a great read! reader friendly and informative.