That with its pixel art is styled so beautifully and so hard to read at the same time. Couldn't read it at all. (It's not an eye vision problem, reading pixel fonts just is quite taxing on the brain).
It's pixel-art styled but not pixel-art arted (is that even a word?). The font does not cleanly align on pixel boundaries on non-HiDPI screens thus it appears blurry. In fact, the whole website appears blurry.
Folks, when making pixel-art styled stuff, ensure they are actually sharp on bix-pixels screen. It's not pixel-art if it's sharp only on your macbook.
I found it hard too. Perhaps the difference with the other people responding is the size the font is rendered. On my screen, the distance between the top of a "d" and the bottom of a "y" in the body text is 7mm. That corresponds to font size 18 in Word, or 22px in the browser, so basically a chapter heading.
I read on a 16” MacBook Pro. Size and display quality were not an issue.
I could have read it entirely with the aliased font, but it triggered me just enough for me to disable it (I’m doing web dev these days, so it took me ~5s; if it would have taken me more I would not have done it).