Of course, I Googled the word and tucked way down past interstitial cystitis, lung disease, and other medical terms, there popped up a couple of gems that were of a creative nature.
The Interstitial Library is hard to explain, but basically there is no firm location or exacting books it holds. In their words, "The Interstitial Library does not aspire to completeness. Indeed, we champion the incomplete, temporary, provisional, circulating and, of course, interstitial. Above all, we aim to acquire and catalog those books that are themselves interstitial: that fall between obvious subject categories; that are notable for qualities seldom recognized by traditional institutions; that no longer exist, do not yet exist, or are entirely imaginary."
Below is the link to the page on their cataloguing rules. Go to the list of examples. Call me an interstitial nerd, but I found them to be quite amusing:
Another website, The Interstitial Arts Foundation - Artists Without Borders, "is a not-for-profit organization dedicated to the study, support, and promotion of interstitial art: literature, music, visual and performance art found in between categories and genres – art that crosses borders." They publish an anthology of works called "Interfictions". These are short stories which fit no particular genre of literature.
I felt validated. The interstitial ideas that dwelled in the spaces of my mind found a sense of connection and like mindedness dwelling in cyberspace. And yet, I don't feel like this is all there is. There is plenty of room to continue to expand and explore - both into the interstitial recesses of the mind and the universe. No, we are not quite done here yet. We are only just getting started...