One of the interesting things about magico-religious systems is that just about anything can be an “in”. A robust system – and an ancient system that lasted a while is going to be pretty robust – is an interconnected whole, and learning how one aspect of it works will inevitably start flowing into the next bit, and the next bit, and the next bit.
I didn’t start writing The Traveller’s Guide to the Duat because I was interested in ancient Egyptian funerary techniques. Far from it – I find death rituals among the least interesting parts of any magical-religious system, and I never got into Egyptophilia when I was younger because mostly what I ran into was people squeeing about mummies and the shiny, shiny funerary furniture of Tutankamen.
But the Book of Going Forth By Day – popularly known as the Egyptian Book of the Dead – is one of the most well-known bits of Egyptian literature. People have been mining it for esoteric meaning since it was translated, and even before. Talking about Egyptian magic inevitably leads to talking about the stuff we can find in funerary literature, because there’s a lot of stuff preserved in funerary literature.
And it’s amazing what you can find when you dive in deep in a specific subfield. Getting anywhere working in depth with the Book of the Dead means understanding the etheric anatomy of a human (and possibly the esoteric meanings of physical anatomy); it means exploring the use and significance of a variety of symbols, some more obscure than others; it means the use of colour, shape, and materials in the crafting of amulets; it means building a comprehension of the geography and nature of the spirit world; it means an overview of shapeshifting the astral body, including into a godform; it means knowing how to treat with and interact with various Powers; it means an analysis of the metaphysics of initiation. In short, there is something for almost any type of magical or spiritual explorer to be found there.
It doesn’t really matter where one starts in the system, because once the explorer strikes bone, it’s a steady course from there to reveal the whole skeleton; once the explorer strikes blood, it’s an inevitable flow from there to the living heart that makes the system whole.