Thanks! after playing with it I finally got it working:
(?P<author>[^-]+)\x20-\x20(?P<title>[^-]+)(?:-\s+\[(?P<series>[^.]+?)(?P<series_index>\d+)?\])?
Successfully parses the following formats:
author - title
author - title - [series]
author - title - [series Number]
author - title - [collection - series Number]
author - title - [collection number - series Number]