There was a time when moving to a new flat ( house ) meant carrying boxes of books and even more boxes of vinyl records. All the vinyl the average music collector had fits nicely on one USB stick with more than enough space left to store all his books, in e-reader format.
Milne did not have to rewrite his books ( maybe he made a few cosmetic changes, I don't know ) to reformat his PDF books for e-readers. Simply because he writes his books in LaTeX. He can publish to PDF in any format, he can have them nicely printed or he can merge his content in a wiki. His mathematical source stays untouched.
One of the things computers can't do yet is scanning a mathematics book, one of Euler's publications for example to LaTeX.
It makes me a bit sad that Windows 8 will be a lot like iOS from the iPhone ( Microsoft wasn't able to leap-frog Apple after Windows 95 ), I mean Windows 8 will be fingers based instead of pen-based. In the 1980s computers were for male geeks, today computers have become social media tools which are mainly used by women. I mean which male doesn't get bored by hanging out on facebook day-in day-out.
Writing mathematics is done with a pencil after which it is typeset.
What makes me sad is that just when pen-computers started to recognize handwritten math ( in Mathematica for example ), the world is flooded with an interface that is essentially geared for Facebook. Lots of pictures and every text has the intelligence of the two thumbs it has been typed with. Writing is just like reading. Very few people ( like to ) do it well. With or without e-reader.