[Adoby]

Sometimes when you add a bunch of books you may by mistake use the wrong import options.

If the books you import are saved from calibre they may consist of a folder for each book, a cover file, one or more actual ebook files and an opf-file with metadata about the book.

Such books should be imported as one book per folder. Then only one book entry is created using the metadata in the opf-file, for all the different book formats.

If it is imported as many books in the same folder then a separate entry is created for each actual ebook file AND one EMPTY book based on the opf-file. So that is one possible reason why you have empty books.

I suspect that you ran an import with the wrong add/import options at one time. You get warnings about duplicate books, but you may have ignored that... Don't do that.

One reason why bad import options are bad is that you may lose the metadata in the opf-file. And you will have to download it again, when all along that data was available but discarded by you. Just imagine how much time you might save for reading if you preserve the metadata in the opf-file.