If you're using the regexp kacir posted earlier, try this modification:
Code:
(?P<author>[^-]+)( - \[?(?P<series>[^-]+)(\[| )*(?P<series_index>[0-9]+)?\]?)? - (?P<title>.+)
That should make the series index optional if series is present.
And go read that tutorial I keep talking about! It's why it's there.