I think the bigger "test" behind this is that maybe some content that you would maybe distribute as an ebook, but that needs hands-on practice for you to really get it, could be effective as this kind of paper handbook/notebook combo
That's what I am trying to find out. Normally it's "Buy the book, get the worksheets for free". What happens if we reverse this: "Buy the practice book, get the eBook for free". Time will tell.
I could also imagine something like those paper organizers from as it seems ages ago. something very flexible.