I find that scientific textbooks (machine learning, etc) are much more usable as books than as pdf, as I need to often jump from one chapter to another and it needs to be the matter of a split second (or I won't bother to look for the information).
I still don't see how a book with text's "realness" helps. I don't see how flat paper with ink printings is "tactile" enough and not in fact just as abstract as any method of digesting information second or third hand (at a computer terminal, reading a newspaper, attending a lecture, etc.) vs. our evolution's first method of information gathering: experience; you know, going outside, feeling a rock, finding your way through town and mapping it out in your head... I'm 24, but I still remember before the internet became what it is today and even then, reading was considered "boring" by everyone other than nerds because, surprise! it was a pretty abstract activity.
I think the real factor is the preference for paper and the learned habits with reading on it. People simply have learned first to "deep read" with books, so they read/learn easier since they can tap those already familiar (perhaps subconcious) habits without having to figure out new ones. Unfortunately, phone and tablet screens are associated with mindless or at least light reading and aversion, not deep cognition, so perhaps that's why there is some observed deficit in reading on them.
Still, I'm going to accept the "science is not quite settled" part of the article. Obviously there is some deficit ninnsome cases but we don't know why.
Math. Students pretty much don't read their textbooks from algebra through calculus. And it's even sadder when you get a student in PDEs or abstract algebra who acts as if reading their textbook would reveal their illiteracy.
This is probably because you can get through many early math classes just by listening to the lectures.
I find that scientific textbooks (machine learning, etc) are much more usable as books than as pdf, as I need to often jump from one chapter to another and it needs to be the matter of a split second (or I won't bother to look for the information).
But perhaps mileage varies.