How to make my published flipping book not available to unauthorized people?

I'm a book seller, so I want to add security on my flipping ebooks, the people without my authority won't access my book. What can I do?

After using "Upload Online" service (what's upload service) to publish your book online, you can enter into "Manage Online Books" window, click "Book Detail" icon to enter into "Modify Book" interface:

You can choose "Share Options" as "Private", which means the book is only available to specified people. Then you are able to input email addresses to authorize viewers.

You can easily add multiple users as follows:
****@gmail.com;****@flipbuilder.com;****@hotmail.com;...

When unauthorized viewers attempt to view your flip book they will be denied access. Users with access will simply enter their email address to view: