Coming from little metaphysical background and trying to latch onto Crowley's work is like leaping up a staircase. It isn't that it is necessarily hard to understand (hint: it's only a paradox because it doesn't make sense to human logic) but that it has a lot of vocabulary you need to be taught or figure out first.
As for what magic (I don't spell it with a "k", because I don't bother to distinguish between actual magic and stage magic) is, I have defined it as "reality's operating system", in which manipulated information and programs are spells and spirits, respectively.