The problem is that US letter paper or A4 are both roughly 14" diagonal, and textbooks and magazines are often a bit larger, so you need something like a borderless 15" diagonal display with at least 300px/in resolution. I'm hoping that within a few years we'll see reasonably-priced tablets with displays like this and with serious battery life (say, 24 hours or so, because thinner isn't everyone's first priority).
