because you always wondered how to make a tetra-tetra-flexagon.

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the diagrams don't give a sense of what the book actually looks like if you aren't familiar.
It is sort of jacob's ladder-esque and you keep folding it open back on itself to reveal 4 diff spreads.
here's a google image result for it...



I think it's just the kind of thing you need to see/make in real life.

link for full directions
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