This document summarizes key aspects of Jeff Speck's book "Walkable City" which outlines a theory of walkability. The theory states that for a walk to be favored, it must satisfy four main conditions: it must be useful, safe, comfortable and interesting. Speck also proposes ten principles to promote walkability in communities, such as putting cars in their place, mixing land uses, protecting pedestrians and planting trees. The document concludes by stating some objectives of creating walkable cities such as providing diverse public spaces and prioritizing pedestrians and cyclists.