An introduction to how cryptocurrencies like bitcoin are just one example of transformative applications that this relatively new technology makes possible. The author interprets the complexity into digestible anecdotes, metaphors, and straightforward descriptions for readers who don't know tech, and explains all of blockchain's most important aspects: why this so-called digital ledger is unhackable and unchangeable; how its distributed nature may transfer power from central entities like banks, government, and corporations to ordinary citizens around the world; and what its widespread use will mean for society as a whole.