One fascinating thing about the Hollow Earth is that it stands with one foot planted in two very different worlds. While many of us were introduced to the concept through pulp science fiction stories, Hollow Earth theory is a real thing that has (or at least had) real adherents and true believers, ranging from John Cleves Symmes to Cyrus Teed and others.

Perhaps the oddest of these is Richard Sharpe Shaver, whose own accounts of the Hollow Earth managed to occupy both realms – published as fiction in magazines such as Amazing Stories in the 1940s, yet maintained by Shaver as absolute truth, an enigma often known as “The Shaver Mystery.”

I haven’t actually read any of Shaver’s accounts. Indeed, my knowledge of the various true believers of the Hollow Earth has mostly been acquired secondhand. I probably first heard about the majority of them from Dr. Frank Baxter, whom the wags at Mystery Science Theater 3000 dubbed “the Gesture Professor,” in his introduction to the 1956 Virgil Vogel movie The Mole People.

(I always liked the eponymous mole people themselves, but the movie – and its depiction of a Sumerian civilization that has become trapped underground – is a bit of a snooze.)

Most of my contemporary knowledge of actual Hollow Earth theory, however, comes from one nonfiction book – one with a simple title, and an unusually long subtitle. Originally published in 2005, David Standish’s Hollow Earth bears the absolutely unwieldy subheading “The Long and Curious History of Imagining Strange Lands, Fantastical Creatures, Advanced Civilizations, and Marvelous Machines Below the Earth’s Surface.”

How could I not love that?

I got a copy of Standish’s book at a secondhand book shop years ago, and it helped to reignite my passion for this odd material – and also teach me about its real-world history. While I had read Walden in college, Standish’s book was also the first time I really noticed the Henry David Thoreau quote that serves as one of the two epigraphs in Notes from Underground.

The implied link between the Hollow Earth and our own personal interiority struck me immediately, and stuck in my head for years. I knew that I wanted to write something that could use that quote as an epigraph, and many false starts followed before we got to the place where we are today.

Epigraphs are supposed to help readers get into the right mindset for a book, and for me, epigraphs often come early in the book process, as I get myself in the right mindset, as well. Such was the case here.

In many ways, the two epigraphs in Notes from Underground serve as the two dominant themes that I wanted to explore in the book – first, the Hollow Earth as a reflection of our own interior worlds, as a mirror for our longing, our questions, our hopes, and our fears.

I think that’s true for the people who really believed in the Hollow Earth, too, to some extent, even if they didn’t always realize it. Most early Hollow Earth theory posits it as a more Utopian ideal – a place where things are, or could be, better than they are here on the surface. In Notes from Underground, those Utopian ideals are present, but they have gone to seed, left to rot and ruin and the slow creep of entropy. “Nothing lasts forever, not even forever.”

For many of these true believers, the Hollow Earth was more than an idea – it was something almost like a religion. Indeed, Hollow Earth churches like and yet unlike the one depicted in “Leandra’s Story” really existed, with the best-known among them being Cyrus Teed’s “Koreshan Unity,” the last known member of which passed away as recently as 1982.

Like many of the characters in Notes from Underground, these people longed for something more than the world of the surface. Some of them yearned for it so strongly that it carried them to their graves.

How could that not show up in Notes from Underground, at least a little bit?