I just finished reading the first Dune book¹ which I enjoyed a lot. The book does a fantastic job exploring political science, power, specialization, primitives vs moderns, gender powers, and intra/interpersonal psychology but I was teased by the few mentions of hard science - desertification, spice formation, worm biology, genetics, water reclamation, and fremen economics.

Are any of the other original six books known for exploring the hard science more? Or, any of the dozens of books that Herbert's son directed?

Also, I don't know if it's been discussed anywhere, but the Fremen appear to use water as a store of value. The water is kept in a full reserve "tank" at a variety of sietches with rings used like bank notes representing some direct relationship to the deposited water. I believe these rings are the fremen's medium of exchange. It's unclear though, at least based on my reading, if the rings are claims on future water withdrawals or are merely a kind of proof-of-work for minting rings. Does anyone know?

It's also curious that fremen don't use spice as money considering they frequently trade it for other things and it's probably easier to store. Money for them appears to follow the law of the minimum - water is their most scarce biological dependency. I can't tell immediately if Bitcoin is doing something similar by minting money using energy, which is in high demand, the opposite because energy is also in high supply, or something unrelated.