I had the idea that the written books would come in PDF or something like that, in a very very economical format, because so many books or courses are generated that the bookstores simply do not sell any more, they all have old books on the counter, so for the programmers It would be great to have a book delivery point somewhere in the city where it could be printed at a low cost PER UNIT (paying minimum copyright), in reality printed books are much better than pdfs for learning.