This is a return to the earlier style of books where the plot is only there to ferry you from one joke to the next. The dungeon dimensions don't really serve much purpose other than to add some "boding" as Gaspode would call it. I guess also to be able to wrap it all up in the end so that Holy Wood doesn't exist again.

Gaspode the Wonder Dog stole every scene he was in, brilliant character. It was also the introduction of Mustrum Ridcully and Ponder Stibbons.

I think this might be the first mention of Headology as well, although interestingly it's by the Wizards when making their real beards appear fake with wires.