This is probably a lot more useful in Japan as it explains a lot of Western/UK customs, but as a person living in the US who is familiar with most of these customs and holidays, the majority of the content in this volume is unnecessary. I had hoped it would focus more on the mythos behind the stories or the mythos that couldn't fit into the previous volumes, but what's explored is primarily background info that inspired the series rather than the series's folklore.
While the discussion sections were interesting, the actual panel-by-panel information often felt pointless or seemed too straight-forward for an explanation.