I don’t remember that book having many fluffy parables. A lot of it was the kind of implementation detail he would talk through in person with a coaching client. I would think most people looking for that kind of help would rather just use the time it takes to read a full book to help them think through their personal situation.

I would strongly disagree. The Book teaches you not only a system of organisation but also how to think about tasks and organisation in general. The system can be broken down into 20 pages. The general thinking around it cannot easily be condensed as much. It has helped me a lot beyond GTD because the same principles can be applied in other contexts such as agile dev work or organising a company.