Winchester's just using hyperbole when he says books are "about" to vanish. Or maybe he's thinking in terms of a slightly different time-scale from most of us. He's quite old, you know, and he
was trained as geologist.
I don't think we'll see printed
novels phased out for while to come, at least– and then it'll be because e-readers of the future will come to
match printed books in ease of reading, aesthetic appeal, cheapness etc. You know, so it'll be
just like reading a book (only with a search function and everything). What we have now is the very first, expensive, primitive version of the technology– it won't stay like that.
Reference books are another matter. As someone already pointed out, they're already more convenient in digital format. Also OED, Encyclopaedia Brittanica and similar works have always been beyond the means of most people anyway, so it's not like anyone is going to be suddenly deprived of them through not being able to afford an i-pad.