Molnar on the Tweleve forum recently published his solution to this puzzle. I asked Molnar if I could share it here. He said sure go ahead. What a neat puzzle!
I will agree with the author's statement that the code is simple, once you know what is important. Both the colors of the sides and the triangles themselves are distracters. The only thing that matters is the locations of the vertices. The first thing to note is that the vertices are evenly spaced in the vertical direction. This implies a grid structure. One can construct a grid, with cells of size 20 pixels by 20 pixels, and overlay it on top of the triangles image, such that each vertex is in the center of a cell (within a +/- 2 pixel drawing error). Having done that, the vertices have a spread of 26 cells horizontally and 30 cells vertically, with each row of the grid containing one vertex. See the link below for an image.
Taking the columns to represent letters of the alphabet, the vertices then spell out a message from top to bottom: KNAJYMTZXFSIFSILTQIHTNSUQZXTSJ. This, of course, is not very helpful. But given how well the grid fits this drawing, it is assuredly the correct extraction method. So we look to see if this is some type of ciphertext. And after a bit of experimenting, one can see that a backwards shift of 5 gives the text: FIVETHOUSANDANDGOLDCOINPLUSONE. Why the extra step? Reasons, I guess. One could have come to this answer straight away by starting the alphabet used in the grid with a "V" instead of an "A", but I saw no cluing to that effect in the text that accompanied the image.
Anyway, it's not exactly clear how to interpret FIVE THOUSAND AND GOLD COIN PLUS ONE.
Very clever. I shall have to remember this trick for future reference; some other hunt-maker might re-use it.
Did anyone figure out what the author meant when he said "whatever you do, don't apply this to a certain page in the book!"? Seems like the most likely page would be the huge grid with all the numbers and letters and symbols, but I can't get anything meaningful out of it.