Based on my quick skimming it's mostly a mathematical writing with modeling of the oscillators one might find in biology like neuronal populations, or gene expression based clocks, or calcium waves through gap junctions in the heart, etc. It does not seem to be pseudo science like the linked wikipedia article. But it's not down in the weeds biology either, it's abstract.

If anyone else is having trouble with their hosted "App to read (PDF)" that's not actually a pdf, the 1988 first edition pdf of the book is on libgen. If you don't know what libgen is or how to get there wikipedia will tell you.