REGEX = Regular Expression (
The Wiki has some info on learning it)
You use REGEX here to create patterns (suitable to your input source) that you can
capture and Manipulate.
You have 3 things you want to Capture
Title
Series name
Series Index (numeric only) ignoring 'Book #'
You are going to put \2 (the second captured item) into {series}
You are going to put \3 (the second captured item) into {series-index}
Then you want \1 into {title}
The \# are the captures L->R