Like a lot of academics, I’m sure, I got this email the other day, from a textbook publisher doing its best — like all those MOOC providers and other eBook developers — to create the impression of a need.

Funny, but I thought we’d already invented a way to have an individualized reading experience.

Optional marginalia and yellow highlighting take it to a whole new, hypertextual level, of course.

And it never needs recharging.