[BetterRed]

@Inukami - I import into an "Intake" library, where I do adjustments to metadata - e.g. move subtitles into a custom column, remove and add tags, set custom columns, etc, and then use the Find Library Duplicate feature of the Find Duplications plugin to help identify duplicates between the "Intake" and "Target" libraries. Non-duplicate books are moved to a "Target" library

Originally Posted by Inukami

[*]You have changed the title of the book so Calibre doesn’t find that you have two version. You can use the find duplicates plugin.

I do my standard adjustments (strip subtitles, apply AP Title style rules) before I get to running FD->FLD, so "Fuzzy" matching will usually find them.

Originally Posted by Inukami

[*]Metadata does not match or different

If the changed metadata changes were relevant to me then I would manually change what I have

Originally Posted by Inukami

[*]Cover is different and you prefer to keep the current cover

I would keep the original, if I wanted to keep the 'new' cover I would put it in a multi-image TIFF (creating it, if needs be) which I would keep in book folder as a 'format' file.

Originally Posted by Inukami

[*]Do you import another version and edit the new one and delete the older version? But if you do that, it is a lot of work doing the metadata again?

I never delete the original, see previous answers regarding metadata and cover, and the following answer regarding the format files

Originally Posted by Inukami

[*]What do you do when the book content changes but the metadata is the same? Can you transfer the metadata from the old version to the new and then delete the old?

If I wanted to replace the existing content, I would first copy the book from the "Target" library to an "Archive" library, and then make an entry to that effect in the book's Notes custom column, and then I would drag-drop the new content file into Book Details panel of the book in the "Target" library.

If I wanted to keep the existing content, but not throw away the new content, I would do the same except I would drag-drop the new content file into Book Details panel of the book in the "Archive" library.

On most occasions I simply replace the existing content with the new content by dragging it into the book's Detail panel (left right sidebar).

BR