crich70 - if the author name & title are in the book file names and its a consistent pattern then it ought be possible for us to help you with a Regular Expression
eg it would be
(?P<author>[^_]+) - (?P<title>.+) if the file names were thus:
Felicia Gangtree - 17th century food in Ruthenia.txt
Felicia Gangtree - Wine growing in Upper Silesia.txt
If the books are something like epubs or PDFs you might be able to extract the author names from there when the books are added,
If you want to try either of those ideas you'd have to delete a couple of "unknown" books and re-add them, otherwise you could get duplicates,
Late Breaking Thought - if the books have an ISBN written in them, then you could use this plugin
[GUI Plugin] Extract ISBN to extract it and pop into the database and then download the metadata from the net - including the author(s). Install the plug in, make sure its in your tool bar, select all the "unknown" books and hit the tool bar button. Then search for books with
identifiers:true and do a bulk metadata download for those books - with a bit of luck, job done.
BR