My sense, which admittedly comes from reading most if not all of Three Pound Brain, is that it is important if not essential to a sound understanding of the Second Apocalypse:
"Storytelling is my primary means of sounding these darker possibilities. The centerpiece of my project is The Second Apocalypse, the tale of a monastic outcast who rises from obscurity to shake the world. Through flawed gazes and broken hearts I try to paint a canvas as savage and sage as those rendered by my adolescent idols, Howard, Herbert, and Tolkien. I’ve lived with this story for thirty years now (!) and I’m pretty sure I’ll never have a better one to tell. “Perhaps the best fantasy series written in the past decade…” The Atlantic.com recently declared. And I’m just getting to the interesting bits now.
Three Pound Brain is my secondary means of sounding these questions, a kind of philosophical scrapbook where I try to make theoretical sense of what seems to be happening—the nature of the biological, social, and technological processes behind our ongoing ‘semantic apocalypse.’" (From the 'About' page of Three Pound Brain)
I think the thirty-year story reached its conclusion with the destruction of the Great Ordeal. With "The No-God" he is going to have to go beyond what he dreamed up as a teenager, thus the 'discovery.' I think Three Pound Brain gives a sense of how Scott sees the world becoming, and to the extent that he sees both Earwa and this world coming to apocalypse it sees likely that he sees them converging. I expect Earwa to become disenchanted. I would not be surprised if by the end of this next cycle of books Earwa is mundane , in the Xanth sense of the word. The events of the Second Apocalypse would become Scripture, but as can be the case with (for example) the Bible and the Koran, misremembered or misconstrued.