I find keeping track of "context" is much easier with a real book. For example, I know that I saw an equation 3 or 4 pages ago on the top left, so I can quickly

I find keeping track of "context" is much easier with a real book. For example, I know that I saw an equation 3 or 4 pages ago on the top left, so I can quickly flip back and find it, whereas on a digital form a would have to PGUP a couple of times and be presented with a "blur" of pixels and try to catch the same equation. Then again, I'm not sure what UI modern eBook readers have for setting and going to bookmarks.