> I think tablets are a decent secondary substitute for print-form [...] where the activity is more browsing rather than linear.

Interesting that my impression is more or less the opposite: I can read on a tablet all right, but leafing through is annoying and switching back and forth between three or four places in a big (thousand-page) reference book is so annoying as to be nearly impossible. The first, because rendering PDF pages (understandably) takes time, and the second, because I’ve seen no bookmarks interface as seamless and convenient as leaving a loose sheet of paper or even just your finger in the necessary place—they’re all much too fiddly.