Start with The Death and Life of Great American Cities by Jane Jacobs. Most modern books on the topic reference this fundamental work from Jane's time living in New York City. Jeff Speck continues the story started by Jane in Walkable City. In Streetfight, Janette Sadik-Khan offers a glimpse into the rapid evolution of bicycling coming out of NYC and the backlash it has caused. And Instant City by Steve Inskeep offers a rare perspective through the lens of Karachi, Pakistan.