I think a big piece of that was that the physical learning materials let you skip over stuff, but you still had to lug around the skipped-over stuff, so you never really stopped being reminded that it was there, and probably were able to return to it should it suit you.

(Of course, I also hold the opinion that the best learning materials are pretty modular, and very clear about what you're getting, and those go hand-in-hand. I think most things these days are not clear enough about what they are, and that's a problem.)

I could not agree more actually. I personally feel like we've lost a great deal. Having a good book that has been carefully and logically constructed, checked, and reviewed is the best.

Perhaps with AI, we'll be able to generate books? Certainly that is far off, but what an amazing thing that would be!

It's not far off at all, some people sold AI-generated books on Amazon (they banned them in theory). Good and/or factual books however... Who knows.