Here's what I found in the detailed report of Collections Plugin:
Quote:
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Books listed as "Book with no file" indicate books found in a collection that do not have a file on the Kindle filesystem (or are empty) and therefore the title is not known. Either the book is an Internal Kindle file (like a dictionary) which is okay, or it is a book that has been deleted but left in a collection - you can use Edit Collections to remove it.
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