Here is a simple card trick.
Take a deck of cards. Squeeze them down on a flat surface. Break it in half. Leave the bottom half on the table. Now look at the card and set the deck back together. For the trick, push the side of the top half of the deck.
It should slide at the break and reveal your card.
This is also how you can find your page if you accident my close a book. It works quite often.
I believe this is part of the force holding the phone books together...
I set up a simple experiment to test the question if there are more forces at work than static friction. The experiment was one notebook, the clamping notebook, sat along the edge of a table and another notebook, hanging notebook, hung from it by a sheet sandwiched near the bottom of the clamp. The clamp was secured by its spiral using some pens and tape.
I can go over the physics, if you like, but I had calculated it would take the whole weight of the clamping notebook to hold the hanging notebook in place. It turned out to be much less, only 20/78 of a notebook. There appeared to be a force equal to that of static friction (assuming a standard coefficient of static friction for paper) that was unaccounted for.
I think what best explains this is whatever explains the anecdote of the card trick. There must be some kind of air pressure missing from the air being squeezed out between the pages.
I noticed it a great deal in the experiment, the first time the hanging notebook slipped out there was 16 pages pressing down on it. It stood stationary a few seconds before falling. Lower amounts of pages also held but only for a few seconds. It had a consistent delay, even when only one sheet and the cover clamped on it, very little weight, after pressing down there was a several second delay (while air was drawn in) before the notebook slipped outright.
EDIT: There seems to be some claim that 1.0 is a reasonable assumption for the coefficient of friction for paper. By looking at several sources online I found the coefficient of friction seemed to be close to 0.55 and used that for my theoretical baseline.
This is important because I calculated a coefficient of friction from my tests of 0.995, so that is why I concluded there was another force at work. Here is one of the sources: http://www.tappi.org/content/tag/sarg/t549.pdf
This seemed to agree with a search, for example Fuji printers says it is between 0.7 and 0.4. An average of 0.55, exactly what I went with.
Again, in my experiment there is no "binding", both literally and figuratively, so there is an additional force, other than static friction, that nearly doubles the holding power.