As Tim said, Safari is actually both (2000+ on-demand video courses plus all the books and a bunch of conference videos). And in our usage data, we see most peo

As Tim said, Safari is actually both (2000+ on-demand video courses plus all the books and a bunch of conference videos). And in our usage data, we see most people do both things -- short "ad hoc" learning, especially during the work day, with longer sessions of activity, both in video and books, in the evenings. The trend is especially pronounced with mobile devices, as mobile usage peaks on the weekend and includes a much longer average session length than we see on the desktop.