The calibre writeup is indeed readable, and entertaining as well.
However,
http://Regular-Expressions.info has a much more comprehensive writeup, as it is an exhaustive guide, and I find that to be more useful on a personal level.
Additionally, my regex guide of choice has a pretty readable format as well, and I feel no need to switch mental tracks when offering regex suggestions (depending on the complexity of the matter) in order to *patronize* calibre's guide.
At the end of the day, either one can give you a basic rundown on the regex approach, which is what matters.
