The thing is, ISBNs aren't hierarchical --- they are bought in blocks (or even individually at an exorbitant markup, says the guy who bought one to reprint a single book), so this doesn't show anything really interesting/useful. A visualization using LoC or even Dewey Decimal would be far more useful, esp. if it also linked to public domain and copyright-free repositories/lists, say an interactive and visual version…
ISBN's are hierarchical, what do you mean? Like Gaul, ISBNs are divided into multiple parts, where one part is for the language, another is for the publisher, and the last is for the title. The last part is a checksum. https://en.wikipedia.org/wiki/ISBN#Overview
One can't use ISBNs alone to create a hierarchical listing of texts which is useful for anything beyond browsing by language/publisher/order in which the ISBN was generated.
A visual and interactive representation of books by LoC or some other cataloging system would actually be useful.