It's not :(. Although the average person could probably get a lot of good high-level info by browsing it.
I haven't yet come across anything that is a good gentle intro. Most resources that approach music and math make the mistake of treating music theory like the law, without any rationale for it provided. Music history textbooks typically give a lot more context of how our music theories emerged, but they don't talk about why that might be, based on acoustics, psychoacoustic, and math.
Maybe one day, I'll write the comprehensive intro I wish I'd had.
Oh most definitely! I'd describe it as an extension of what's taught in the standard music theory curriculum. It makes the very ambitious claim of developing a framework that can be used to analyze all tonal music, from the renaissance to the present.
You need something like this: https://www.amazon.com/Alfreds-Essentials-Music-Theory-Self-...
It's not something you're going to learn in an afternoon or a weekend, it's hard work and Beethoven was still working on it at the end of his life.
Last month I spent an evening analyzing and discussing a passage of Rachmaninoff, trying to understand how he knew how to write a certain sequence.