Rory Highside has written a fantastic article diving deeper into proof of work with the following topics:
Consensus & The Byzantine Generals Problem.
Proof-of-Work and Competition.
Proof-of-Work economically incentivizes Bitcoin to become the ultimate arbiter of truth.
The symbiotic relationship miners have with Bitcoin.
World Kilowatt Dollars.
Bitcoin Time-Energy Accounting and Thermodynamics.
The Bitcoin Metabolism.
Read his monumental article here: