I think a lot of the ways that Schillinger thinks about music is outdated. It makes sense considering when he lived. Basically it comes down to this semi-serialism type deal where he breaks some element of music down into a handful of distinct parts. Then labels them with numbers which you can implement as a form of vector in your music.
Not very practical for analysis, its a very specific way of writing music and its not even that good (at least for some chapters. Other chapters have potential though). But the underlying thinking is interesting