Recovering deleted PDF brochures from iCloud Books app on iPad

I went to iCloud and try and recover some storage as it was full. I selected the Book app and deleted all the files there thinking it’s a backup copy to iCloud. However I now found my Book on iPad has no more files in the library. Is there a way to restore all of them back easily. Note most are pdf brochures and not ebook purchased

[Re-Titled by Moderator]

Original Title: Apple book in icloud