I love the system (saved my life a couple of times) but I don’t think the book is a good place to start. I’ve read it many times because I’m obsessed with it but it led me down to a couple of bad paths when I was first starting out.
Bad path number one: writing down everything but not processing it properly. Bad path number two: writing down and processing everything but not actually doing the stuff. Bad path number three: having lots and lots of well-organized lists, doing the stuff, and getting stressed and exhausted.
https://idiomdrottning.org/gtd-bad-paths