Exactly why are cities good for you? This is the question one expects to be answered in a book called Cities Are Good for You. Do cities make you live longer? Do they make you happier? Do they make you a more caring person? Which is it? Oddly enough, the book has very little to say about the important claim made in its title. Only on pages 286 and 289 does author Leo Hollis, a Londoner, tell us that people who live in cities do live longer than those who live in suburbs. And the reason for this is not at all profound: If you live in the city, you are more likely to use public transportation. And if you use public transportation, you are going to walk between stations or stops and your final destination. And when you walk more, you burn more energy, and this results in better health. And if you are healthier, you are happier, and if you are happier, you are going to be a nicer person.

The suburbs are car-dependent, and nothing good can come out of sitting in a machine that burns fossil fuel and not the energy stored in your body. "On the relative fitness between young men in inner Atlanta," writes Hollis in reference to research conducted by a professor in Vancouver, BC, "and the city's suburbs, the average city dweller, compelled to walk more often, [is] 10 lbs. lighter than their suburban neighbor." So that's easy enough to understand and, as we see in the book, can be explained in a couple of pages. But Cities is nearly 400 pages. What else is it about?

The main matter, which is written in a very plain style (Cities is no Planet of Slums), provides a decent survey of the hot subjects, places, and figures in current urban thinking. You can even think of Cities as the literary version of Gary Hustwit's 2011 documentary Urbanized. Indeed, a number of the people interviewed in the movie (Jan Gehl, a Danish pro-pedestrian urbanist; Enrique Peñalosa, the former mayor of bicycle friendly Bogotá) and places visited (the High Line in Manhattan, the Dharavi slum in Mumbai) make an appearance in the pages of the book. And if you combine the information in the documentary with the information in the essay, you will be up to date with the current developments, discoveries, and directions of our rapidly urbanizing species.

"In 2009, the journalist David Owen revealed the astonishing truth that living in New York is a more environmentally friendly lifestyle than living in the suburbs or even the countryside," writes Hollis. "He showed that, contrary to most assumptions, when people live in close proximity to each other, in a walkable environment, they actually become far more environmentally efficient." No book about urban life in our times would be complete without a few or, preferably, many words about Owen's masterpiece Green Metropolis. It turned everything Americans thought about the city/rural binary upside down. The city suddenly became not a destroyer of nature but possibly its best hope. If Owen had not been mentioned in Cities (about two pages in all are devoted to him), it would have been a bad sign, an indication that Hollis was not up to snuff and had written the book without adequate preparation. Cities also mentions, but without much depth, an urban thinker often associated with Owen, Edward Glaeser, a neoclassical economist who in 2011 published Triumph of the City: How Our Greatest Invention Makes Us Richer, Smarter, Greener, Healthier, and Happier.

Unlike Hollis, however, Glaeser's book does spend a number of pages providing meat to the claim made in its title. For example, young men who live in the city are simply less likely to kill themselves than those who live in the rural areas: "The suicide rate for younger New Yorkers is about 56 percent of the national average, which reflects the fact that suicides are more common in rural areas. The death rates from suicide in Alaska, Montana, and Wyoming are more than 2.5 times higher than those in Massachusetts, New Jersey, and New York." Why? Because of guns: "Hunting is the strongest predictor of gun ownership in the United States, which explains why youth suicides rise significantly with the number of hunting licenses in a county."

Another star of current urban thinking who appears in Cities is Geoffrey West, a Cambridge-educated physicist who left the standard concerns of his field (particles, gravity, the nature of light) to study animals (why is an elephant more energy efficient than a mouse?) and, most recently, cities (why are big cities more energy efficient than towns?). "West studied how cities developed dynamically as they grew in size: how they changed shape and personality, how interaction intensified with increased levels of density... Already he understood something of the nature of self-organized systems, but he gave it a twist by considering the city as an organic whole—one might think of a beehive or an anthill or even an elephant." Hollis gives West and his ideas five whole pages, which is second only to what is allocated to Jane Jacobs, the current saint of contemporary city thinking. In fact, I have yet to read a book about city planning that does not mention Jacobs, who died in 2006 and is famous for placing people at the center of the built environment.

The best part of the book, however, is the chapter on one of the largest slums in the world, "Walking Dharavi." Here, right in the middle of Cities, the writing even flirts with a little poetry ("This seemed like a strange way to build a city"), and we get good jolt of the kind of writing Hollis's countrymen are famous for, travel writing. We leave the chapter with a sense of the sublime chaos of this fascinating and complex social system. To look on Dharavi is to see a massive engine for the transformation of humans into a brand-new race. recommended