Originally Posted by mornington
Also, on an unrelated note, there's an option to auto-merge records when they're added but no way to do the same thing manually (they can be merged manually, but calibre won't detect them itself). Use case is: Added several eBook files, metadata was incorrect and was corrected (manually or via a download or batch process) and now several are duplicates - same title and author. I'd like calibre to fix that up for me, by making the "auto-merge" code from the "add books" module accessible as a manually-executable command.
1) Make an empty library
2) Make sure the autosort/automerge option is turned on
3) Select all Books
4) Right click and Copy to Library to the empty library. It will autosort/automerge them into the new library.
On a related note, during autosort/automerge, each new book format is added to the existing record without changing the metadata in the existing record in any way. There was a request for the same functionality in the manual Merge operation (Add the book formats from the records being merged, but throw away all metadata and don't screw up the metadata in the first record by adding tags, description or anything else.) I posted a patch to add this function ("Merge only formats" - shortcut Ctrl-M). I'm not sure if Kovid will add it, but if you see it appear on the Merge menu, that's what it does.