Vayikra is the sefer that deals, to a great degree, with korbanos. In many ways, korbanos are almost a "different" type of mitzvah. Just as Torah and tefillah are miztvos, but may rightfully be considered a subsection of miztvos, so too korbanos seem to comprise a "subsection" of the world of mitzvos. Let us consider a few of the many unique features of korbanos:
In order to resolve these issues we need to understand what distinguishes korbanos from mitzvos as a whole. The overarching description of mitzvos is "fulfilling the command of Hashem." It's an act of obedience, the fulfillment of one's duties [albeit one that changes and elevates the person performing the mitzvos.] But korbanos are described as a "doron - gift." The Maharal makes the point many times (see Gevuros 37, Tiferes 70) that a korban is a personal desire to connect to Hashem. The distinction between mitzvos and korbanos is like the difference between a husband supporting his wife as required by marital obligations vs. purchasing a gift as an act of appreciation and love. This is perhaps why the Torah starts its laws of korbanos with the korbanos that are voluntary, as opposed to those that are obligatory. Voluntary korbanos more completely reflect the essential nature of a korban than do those that are obligatory.
Using this perspective, we understand the reason for the unique features of korbanos. Bringing a korban is an act of bonding with HKB"H, and as such, even before there were mandated mitzvos there were korbanos, reflecting man's timeless yearning to reach out and connect to Hashem. As opposed to mandated mitzvos whose primary value lies in the performance of the mitzvah itself, when it comes to a korban the kavana is of paramount importance, much like when giving a gift where "it is the thought that counts."
It is the same point regarding the castigation of Israel for bringing korbanos whilst sinning. It's appropriate for a person to continue supporting his wife even though their relationship is strained. But if a person showers her with gifts while treating her wretchedly, it is a travesty!
This understanding of korbanos inspires us to year for the day when the Beis Hamikdash returns and we can once again offer our "gifts" / selves to Hashem. We will then go from subjects dutifully carrying out their tasks to a loved one eagerly waiting to be embraced! Bimeheira b'yameinu, amen.