This was a great write-up about the author's experience. I, too, have self-published a niche book -- a coloring book with patterns from modern math, starting with Penrose tilings and then heading through totally symmetric self-complementary plane partitions, domino tilings of Aztec diamonds, fully packed loop diagrams, and alternating strand diagrams. Just fun stuff related mostly to statistical mechanics that I see my math friends working with.

I learned some Adobe inDesign to lay it out myself, generated all the images myself with Python, Sage, Tikz, or just drew them in Inkscape. Then I had it printed at a local print shop. That means there was an initial investment, but once I set the right price I could make a (small) profit by just selling them all. The per-price cost when printing 100 is substantially lower than individual copies.

Another difference for me: I have some connections to the local art scene and was able to sell at several art crawls. I think people found it a refreshing counterpoint to the rest of the art -- something nerdy for the nerdy folks, something they could get for a niece who is excited about math or a cousin who is a math teacher.

Marketing is still the hardest thing, for me as for this author. Facebook word-of-mouth has been the best.