The book is held in place by the force you are putting against it. Remove your hand (remove the force) and the book will fall due to gravity.
when you push your hand against a wall the wall is 'pushing' against you that is why you feel your hand being pushed.
Nathan
In the nursery rhyme, it is unclear who pushed Humpty Dumpty off the wall. It is simply stated that Humpty Dumpty had a great fall.
Beat them against a wall until their brains fall out and then you measure it.
it means watch the wall or you will get pushed into it
no the only reason their eyes fall out is because since they are bracosaphalic (have a pushed in face) they need to be walked using a harness rather a color and if it is wearing a collar and it gets pulled to hard they can fall out.
Infront of the sea wall the gradient dips down because the waves are pushed up against the wall and there is a strong backwash so that's why it dips down. This is beach scouring.
The fall of the Berlin Wall
The fall of the Berlin wall -APEX
There is a book called the Fall of Berlin wall which has covered the era from construction to its fall is available online. It has many photos showing its history. Moreover one can easily find pics online as well.
The wall that blocks the passage on the left side of Mordred's underground lab is NOT rock, but dirt. Push against it and it will fall down.
His wife pushed him into the wall.