When you look at any object, you see everything else, too.
If you look at a book, you're looking at the trees its paper is made from, and the ecosystem from which the tree came; the fine machinery it took to make it, the oil extracted from deep underground that coats its dust cover as plastic.
You're looking at the hands the book was designed to fit into, the eyes that the inks were designed to be perceived by, and the mind that the language is meant to be interpreted by.
Every attribute about the book was not caused by anything internal to the book; the book has no inherent existence of "book-ness." Even the book itself is made of innumerable small things (fibers), which themselves are made of innumerable even smaller things (atoms), and even those are reducible to even smaller things (quarks, bozons, subatomic strings; the limits of technology continues to find smaller things). Nothing is irreducible: How much of the book must be ripped out before it's no longer a "book?" The temporary configuration of these innumerable parts is called a "book," but no essence of "book" is keeping the parts together. Since books are temporary, its source must also be temporary, therefore its source is not ultimate reality. The book does not exist independently of anything else in the whole world. Everything in the world determined the book's existence.
That's what is meant by "dependently arisen." And things that are dependently arisen are compared to illusions or dreams, and are not "real," just temporal reality. The condition for ultimate reality is that it is unchanging and can't be destroyed. Only this can we put absolute faith in. To put faith in the temporal is to be in a constant state of insecurity, because it can't be depended upon to stay the same and stay forever.
To delineate one object from another -- one part of the whole reality from another -- is our own interpretation imposed on reality. Because everything is arisen from everything else, with no independent sources, how can anything be divisible? Nothing can be separated from its source. Can you separate a flame from the spark that ignited it? Can you separate a person from their own mother's and father's conception? Can you separate your vision from your eyeballs? A sound from the air it's carried on?
To separate one part of reality from another is to suppose there are two separate universes. But what can contain the two universes except the unity that contains them both, which would still by definition be the whole universe? There can only be one Whole; the Whole of all wholes. And because its existence cannot be set apart from non-existence, it is Hole. That which never existed cannot become non-existent. That which never existed cannot become existant. Ultimately reality has no birth and no death, and therefore no time and no change. This is the Void