I just tested it, this seems to work with both "King, Stephen - The Dark Tower 01 - Gunslinger.txt" and with "J. K. Rowling - Harry Potter and the Goblet of Fire.txt"
Code:
(?P<author>.+?) - ((?P<series>.+) (?P<series_index>\d+) - )?(?P<title>.+)
lemme know if it works for you.
Matt
btw, don't forget that when you test it, the test name needs to end with a ".xxx" i.e. any extension.