How to set multiple-author metadata for an item in iBooks? While I can edit books' author metadata in the list view, I can’t seem to be finding a way to set multiple authors for a single title. Is there any way to do this, so that I can have, let's say, two separate author entities for a book?

defaults read ~/Library/Containers/com.apple.BKAgentService/Data/Documents/iBooks/Books/Books.plist




...,
{
      BKAllocatedSize = 131072;
      BKDisplayName = "An Introduction To Software Architecture";
      BKGeneratedItemId = 409BAEEB1FD9D2272D63E97BFB7CDEBD;
      BKGenerationCount = 3;
      BKInsertionDate = 558100869;
      BKIsLocked = 0;
      artistName = "David Garlan, Mary Shaw";
      explicit = 0;
      isPreview = 0;
      itemName = "An Introduction To Software Architecture";
      metadataMigrationVersion = 20140106;
      modificationDate = "2000-11-13 17:55:48 +0000";
      pageCount = 42;
      path = "/Users/Sepehr/Library/Mobile Documents/iCloud~com~apple~iBooks/Documents/An Introduction To Software Architecture.pdf";
      releaseDate = "2000-11-13 12:55:48 +0000";
      sourcePath = "/Users/Sepehr/Books/An Introduction To Software Architecture.pdf";
      updateDate = "2000-11-13 17:55:48 +0000";
      versionNumber = 0;
},
...


How can I get more than one author added in the metadata for an iBooks document?
All this metadata exists on the filesystem, so you could use the xattr command line to change pretty much anything, but I find the documentation and syntax to be very challenging to get and use.

I would start by trying xattred editor and perhaps the easier tools SearchKey / SearchKeyLight


https://eclecticlight.co/downloads/


The author has a very superb blog explaining why the app was made in the first time and how to use it as well if you don’t get the buttons or features. Think of all these metadata as a key value store. You just name the attribute (like modification date) and then set a value (today’s date or whatever). Same for page count and in your case, the author metadata string type.

Since you are reading the overall catalog, I would focus on changing the metadata in each book one by one (perhaps working on a throwaway ebook or duplicate copy of a book if you don’t have a good backup and restore procedure for the books you store in iCloud).