...P>The key to grappling with Vol. 2 involves two major problems.
First, Marx took capital as irrational, and the capital-labor relation as an anatagonistic relation of domination. So part of the problem with Capital involves explaining how capitalism can even function in the first place. This helps us to grapple with Marx's discussion of circulation sans crisis.
Secondly, think of department one and department two as capital and labor respectively and it makes a lot more sense. As with Vols. 1 and 3, every aspect of Capital is steeped in a description of the antagonistic social relations (class struggle) and the forms in which they appear (form here means 'mode of existence', the way in which the antagonistic social relations make themselves apparent to us.)
The reason that Marx investigates the forms of the underlying social relations has to do with Marx's conception of science. Marx uses the term science to denote thought which critiques, which does not assume that essence and appearance (form and content) mirror each other, but are mediated and therefore distorted and not directly perceived.
As for the people who continue to insist that Marx wrote an alternate economics textbook, wake up. The book is not about economics per se, since Marx felt that the separation of the economic from the political, legal, artistic, etc. was a specific manifestation of the capital-labor relation. He critiques this separation and does so, not through a transhistorical set of 'laws' (as so many claim), but through a critique of bourgeois society's own understanding of itself (most prominently for Marx, via political economy.) For Marx, the 'laws' of capital are the forms of motion of the class struggle, not transhistorical, disembodied rules.
A complete argument can hardly be made here, but do yourself a favor if you wish to make a comment on or engage with Marx: read what Marx says. Like any other worthwhile intellectual, Marx takes a lot of effort (an acquaintance with Hegel helps a lot). Unlike most, Marx really was serious, even (especially) in relation to Das Kapital, that the point is not to understand the world, but to change it. Theory can never resolve the contradictions of the practical world, only revolutionary practice, the self-activity of the working class (most of us), can produce a society based on the 'free association of producers', in which 'the freedom of each is the precondition of the freedom of all'. Hardly the vision of a totalitarian.