@Gunnerp245 - thanks for feeding back. I think I am going to release it as is tonight since no-one has reported an issue, just need to update all the screenshots.
As for the regex, you can take a look at any of the Goodreads examples included with the plugin for what they do which should hopefully help. Point both series and series index at the same text, then use something like these:
Series field: "Include matching text" of: \(([^,\.]+)
Series index field: "Include matching text" of: #([\d\.]+)