An accessible journey through the seam that connects the digital world of the Internet to our physical world. The stack—the conduit between our digital and physical worlds—is the elusive, mysterious, and least-understood part of the Internet. In the five seconds it took you to read that, 100 quadrillion bits of data just whizzed through the stack. Our metaphors—cloud, virtual, cyber—blind us to the incredible reality: The Internet is a physical thing: dingy, wet, and rusty. In The Stack , Amrit Tiwana takes us on a journey through this gritty reality. The book begins with its breathtaking physical layer, laden with geography, luck, and history dating to the Civil War era. Then it shows us how most Internet traffic flows deep undersea as laser beams, not up in the “cloud” via satellites. It goes on to explore how the stack constructs and deconstructs “packets” layer-by-layer, how these packets travel over rickety paths, and how the stack can assimilate stuff that has yet to be invented. Finally, it discusses how we construct resilience out of fragile parts and how quantum computing might affect the stack. Amrit Tiwana is the Fuqua Distinguished Chair of Internet Strategy at the University of Georgia. He previously served on the faculty of Emory University and Iowa State University.