I had no damn idea:
1) It was originally self-published
2) It was originally a serial
3) It was once free
The story unfolded as a serial over the course of several years. At the request of fans, Weir repackaged it in an e-reader version. Some readers struggled with the downloading process, so Weir then put it on sale at Amazon via Kindle Direct Publishing, charging the required minimum of 99 cents per copy. More people downloaded it at that price than had ever downloaded it for free. They gave it positive reviews.
Not a single damn person in my bookish Twitterstream ever mentioned it to me.
And you would think Amazon would have pimped the shit out of it. They fell down on this job!
— thanks to @JulietaLionetti