It is drenched in flavor and the tone is great. Therefore, it is unfortunate to say that some narrative choices were confusing.
The long second collapsible explaining the anomaly in detail was at points satisfyingly visual, but at others dragged out and dull. I could while reading realize that much of the detail was going to be irrelevant in the future, so it just became a dump of useless exposition.
The third collapsible, while confident in what it is trying to say, suffers from its format. It's moby dick without Ahab's inner. While it can be done, using a character foreign to Bloxham makes the descent into insanity less clear and impactful, as we do not know how Mr. Blox acts before these events.