It's appealing intellectually; I like small and simple models. I suppose if we see a major dislocation in the Chinese economy in the next 2-3 years, his model will be extra-confirmed. (That's a major point he makes on his blog.)
Pettis doesn't really give a primer; he discusses lots of different issues through the same lens, and his target audience appears to be readers with at least an undergraduate understanding of economics and a passing familiarity with balance sheets (I had neither). Frankly, I picked it up via muscle memory (and lots of context-Googling; Wikipedia helps, and StackOverflow has a surprising amount of basic economics info).
I think the bottom line is this: if you're willing to devote a few hours (maybe low tens of hours) to slogging through his posts, occasionally re-reading them a few times and searching elsewhere for explanation of terms, you'll start to understand his balance-sheet theory of macro. And it doesn't require much context, to be honest: one of the beauties of his framework is it glosses over so much of the complexity of an economy by dealing with clear and clean abstractions at the national level. (It's only an okay source for understanding the internal dynamics of an economy; the blog really mostly focuses on international macro.)
I hope that helps... though acknowledge it might not! (My interest was driven by a burning desire to understand WTF just happened!?! circa 2008; that motivation is probably hard to conjure without context, to be honest.)