I generally have four or five books open around the house--I live alone; I can do this--and they are not books on the same subject. They don't relate to each other in any particular way, and the ideas they present bounce off one another. And I like this effect. I also listen to audio-books, and I'll go out for my morning walk with tapes from two very different audio-books, and let those ideas bounce off each other, simmer, reproduce in some odd way, so that I come up with ideas that I might not have come up with if I had simply stuck to one book until I was done with it and then gone and picked up another.
So, I guess, in that way, I'm using a kind of primitive hypertext.