The Bitcoin whitepaper. It started my curiosity in the computer security industry (employed for 5 years now) and the rabbithole of trying to understand every design decision behind the cryptosystem.
[0] https://www.cs.cmu.edu/~rdriley/487/papers/Thompson_1984_Ref...
Even if you argue that Bitcoin as it has evolved has flaws, it is the best implementation we’ve come up with so far. Like democracy, it isn’t perfect but it is much better for its use case than anything else we have come up with to date.
You miss something only when it's gone.