AFAIK you can only do that one-by-one.
1. Install Quality Check plugin and check for Authors with commas. This will show all the books where you have LN, FN.
2. Fix author in Edit Metadata (or in main GUI, if you are confident)
3. In case of several books by same incorrect author, try Manage Authors and check the results. If incorrect author is still present, you probably must fix it in Edit Metadata screen for every book.
4. (If you have some cases with LN FN, you have to find them manually)
5. Don't add any more books until you've fixed things and learned how to avoid those mistakes in the future (like, add books in small batches and always check the results)
How do you know that Calibre has two separate folders? You must have peeked into file folders! (*points accusing finger*). As long as you know not to touch anything there, you are forgiven, but keep in mind that it's the easiest way to break your library.
PS - check out unboggling's thread for new Calibre users, 'How I manage Calibre' or something like that.
And welcome to MobileRead!
Last edited by travger; 09-09-2012 at 02:15 AM.