My first time through "The Negative" was both confusing and illuminating. I agree ZS books are helpful and should be read, but they don't necessarily make sense the first time or two through.
There are good and bad books on the zone system. The Adam's books are better than some which read more like Zen than photography. But what you need to know is there. Don't try to digest a book as a whole, only when you felly understand a section should you go on to the next.
A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.