What constitutes a community? Greater Los Angeles has been known for decades for its iconic freeway gridlock, two-car families and high-rise buildings atop massive parking structures. In 1990 the author, a single mother with a daughter at college on the East Coast, was boarding a transit bus at 4:35 AM in downtown L.A., five mornings a week. The joy of living had become only a distant memory in this darkest winter of her life, but she was always at the bus stop on time, determinedly headed for work in Santa Monica: Head down, always carrying a book (what, after all, could you do but read,...