Friction

When the rice is inside the bottle, there are grains next to one another, but there is a little bit of space, an air pocket, in between each grain and its neighbor Which allows the chop stick to slide out of the bottle. When the rice is packedmore tightly, the friction between each piece of rice and its nearest neighbors increased. At some point, the friction between the chop stick, rice and bottle was so great that it is strong enough to resist slipping and pick up the bottle.

All that is holding the two books together is friction.  This is the same force that acts to stop you sliding a book across a table. When you interleave the two books there is a small force pulling the two books together created by the spine of the book.a table.  This compressive force will create a frictional force between every place the pages are interleaved, if there are 50 interleavings a small frictional force will be multiplied by 50 to create a huge force that you can't overcome with pure muscle.