The node system logic is straightforward, most parameters (val) require an input between black and white (0-100%); some (color) have three values (rgb or xyz).
Going from there you can use the math nodes to get nearly any effect you want.
All the properties in the material node can be independently mixed, so you can use masks to get different qualities on different areas.
Studying the examples in this thread helps a lot.
Problems arise from missing shaders (volumetric emission, absorption and scattering, single sheet translucency etc) and missing properties of the state node like ray length, local and global position and rotation etc.
Especially the fractals are great, when I try to create something similar in blender and take up its musgrave texture I always fail