Those projects might need a lot planning but not necessarily next actions for me. What I would do is just collect information about a Mac and store it in evernote tagged as "bought a mac". Then if I need a more structured higher level planning I would make a mind map. Define my needs, all options, etc. etc. That's it.Also both of those projects, buy a mac and write a book are exactly the sort of project that cries out for the structured approach of GTD. For me those are not simple projects I can do without planning. I'm actually doing both of those projects right now!. Buy a Mac (not macbook but same idea) is on my project list. I used the GTD process to define my needs, do some research including estimating when Apple will do a refresh of the iMac line and am currently waiting for that to happen, probably in late fall.
Write a book is even more critical to define. I have plots to track, timelines, characters and more. All of that fits neatly into a GTD system of next actions, for example right now I have a research task, an update the timeline task, a flesh out character description for character X task and a review sub-plot task for my book. Just an amorphous pile of reference material isn't sufficient to keep me moving forward on that project at all.
I wouldn't define and write down next actions at all. I would just go naturally with the flow, collect the data and see where it takes me. Next actions are so obvious, it's something I generate on the go. Yes, I do use my brain but it doesn't take much mental effort to realize that the next thing to do is to goole this or that, etc. I don't need it explicity spelled out for me in a list.
Same thing with the book, the project needs a lot of thinking and planning but it doesn't need next actions (for me).
It'd be enough for me... It doesn't have to be amorphous though, it could be a very structured and very organised reference (mind map and notes)Just an amorphous pile of reference material isn't sufficient to keep me moving forward on that project at all.