My guess is that it is more than just visual clues on the page and facing page currently visible. I suspect it is also the 3D layout of the pages in space, and how that changes as you go though the book.
With a book, it feels different when reading material at different places in the book. Even if I'm not going through the book linearly but instead looking up things in the index and jumping to them, I get a sense of where things are in space. Later, if I'm trying to find something again I can usually go to close to the right place without bothering with the index.
I suspect that the reason for this is is related to why/how the method of loci [1] (AKA memory palace) works. We are really good at remembering spatial relationships, and the book lets us tap into that.
It might. I'd expect that the effect would be stronger with a physical book because more senses are involved. With the physical book you not only have the visual difference in how the book looks depending on how far into it you, you also can feel a different weight distribution.
With a book, it feels different when reading material at different places in the book. Even if I'm not going through the book linearly but instead looking up things in the index and jumping to them, I get a sense of where things are in space. Later, if I'm trying to find something again I can usually go to close to the right place without bothering with the index.
I suspect that the reason for this is is related to why/how the method of loci [1] (AKA memory palace) works. We are really good at remembering spatial relationships, and the book lets us tap into that.
[1] https://en.wikipedia.org/wiki/Method_of_loci