I had a similar experience with a second-hand copy of House of Leaves [0].

This was a special treat because the book itself already uses copious footnotes and cross-references from fictional characters to create a maze. And now a real person added to the effect by trying to make sense of it themselves.

[0]: https://en.wikipedia.org/wiki/House_of_Leaves

You obviously need to add your own footnotes trying to make sense of those footnotes, then anonymously donate it to a used bookstore.