Very sad that none of the fragment shader experts have written a book focusing on generative art. The Book of Shaders is very basic. How to create something like this (including sound!) while thinking on a per color x,y basis is mind boggling. https://www.shadertoy.com/view/XsfXD2
A good example is the Revision 2021 semi-finals[1]. The entire video is worth watching, but I especially recommend watching the last half of evvvil-vs-flopine (from about 43:00); the last few minutes (from ~56:00) fundamentally changed my understanding of what is possible in a fragment shader. Ray marching into a hand crafted signed distance field is such a bizarre way of thinking about a scene.
[1] https://www.youtube.com/watch?v=NBdRfFwuP40
edit: corrected 'last few minutes' time