"(For paper-based materials.) A textbook that is focused is short. For example, by design Japanese textbooks have less than one page per lesson. Elementary textbooks should be less than 200 pages, middle and secondary less than 500 pages."
This proposal, which in my opinion is highly unlikely to be implemented, would be an excellent start for stemming the continuing pseudo-education of American students and for putting the doorstop-publishing hucksters out of business.