Q: How change authors or others metadatas of the books in ibooks on Yosemite

How to edit book information in iBooks for Mac - Apple Support

That way may or may not save the data with the file (I've heard various).  I have no idea since I deleted iBooks as soon as I saw that it was back (a bit late, lost a lot of books somehow).  I prefer to use Calibre to edit the metadata (author, cover, categories, etc) and resave the book with the new data. It should stay that way no matter what program you use to catalog and/or read.  I know that I made a lot of changes in iTunes and a lot of that doesn't transfer over to my iPad, while data fixed with Calibre will transfer over.