Code: The Hidden Language of Computer Hardware and Software - Charles Petzold

Charles Petzold is also the author of The Annotated Turing: A Guided Tour through Alan Turing's Historic Paper on Computability and the Turing Machine (Wiley, 2008). He wrote a bunch of other books too, but they're mostly about programming applications for Microsoft Windows, and they're all obsolete now. He lives in New York City with his wife, historian and novelist Deirdre Sinnott, and two cats named Honey and Heidi. His website is www.charlespetzold.com.