Changing Metadata of an Epub in iBooks
Just started using iBooks on Mac tonight. I was worried about the same thing.

Here's what works:


Go to List view in iBooks »
Click once on a book (anywhere on the line) »
Wait a couple of seconds »
Click once on the data that you want to change or enter »
That entry will become editable


You can edit anything: Title, Author, Category, etc. Voilà!