At first glance, Book page content looks exactly the same as Basic page.

In fact, if you just fill out the standard node entity fields, Title and Body...

...then hit the Save button, Book page content acts exactly like Basic page content.

What separates Book page content from other content types is the fact that you can easily set it up to automatically contain related, typically hierarchical, content.

To do this, while editing a Book page submisison form:

Click into the Book outline tab

Book field = <create new book>

Click the Save button

Your Book page content will then display an Add child page link at the bottom.

We are now introduced to the built-in structural functionality of Books.