Originally Posted by BoyWombat
It looks like just updating the cover in "Edit metadata" should do it, but it doesnt. Calibre now shows the new cover, but doesnt actually update the ePub! It doesnt tell you anywhere its not updating the ePub.
Its not in the FAQ.
In fact everything in the help section would make you think you only had to edit the metadata via the menus, but its not true.
It actually looks like you need to manually save the file as another version to pickup the changes - which just seems crazy! Why do we have to go through all that, having either multiple copies of the same file, or risking screwing up a nicely formatted ePub by 're-converting' over the top of it!
Am I missing something, or is changing the cover this counter-intuitive?
You are not meant to ever manually extract files from the Calibre library folders by accessing the files outside Calibre. If you do it using one of the recommended ways (such as Save to Disk, or Send to Device) then the file WILL be updated. As you found simply changing it via the metadata editor has not actually changed it in the underlying ebook file held within the Calibre library folders.
Part of the reason for this is that the process of updating a cover is potentially destructive, so Calibre does not change its own internal copy unless it really has to or unless you explicitly tell it do do so.