The publication hub in your Handbooks module is where you have an overview of your handbook(s) and it's always the first page you'll see when you enter the handbook module.
You have two different views of the Publication Hub that you can switch between - process and list view, located next to the button where you add new handbook, as shown in the screenshot below.
The process view
This is the view where you easily can figure out the different statuses of your handbooks, divided into three different categories; "Not started", "Being worked on" and "Finished". A quick explanation of the three different statuses:
Not started are the handbooks that have just been added, but that doesn't have any content yet.
Being worked are handbooks with content added, that has yet to be published.
Finished are the handbooks with content, that is published to your organization.
The list view
This is a slightly more detailed table-version of the process view where you can get information such as the version, the status and when a certain handbook was lastly updated. You always have a filter option on your left at the top here where you can filter on the names and statuses of your handbooks.
Remember that you can always change the number of items per page in the bottom left corner, highlighted with the filtering option in this screenshot: