Thanks for your comment.
Yes, you can add more book or delete the book in the backend.
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Thanks for your comment. It's our pleasure to support you.
I would like to give you the answer for your question as below:
In many cases, the book contents were saved under many formats such as ePub, PDF format, not be saved in the database. We are afraid that we could make this request for you because of our limited technology. Hope you could understand for us.
A regular license allows an item to be used in one project for either personal or commercial use by you or on behalf of a client. The item cannot be offered for resale either on its own or as part of a project. Distribution of source files is not permitted.
An extended license allows an item to be used in unlimited projects for either personal or commercial use. The item cannot be offered for resale "as-is". It is allowed to distribute/sublicense the source files as part of a larger project.