'Cities Are Good for You' - or haven't you heard? Leo Hollis should have had me at the title. His book "Cities Are Good for You: The Genius of the Metropolis" seeks to articulate something I take as an article of faith: Cities are the only place to live. And yet, even the title highlights some of the problems with this uneven inquiry into urban life. It might have been radical to champion the city 30 years ago, when crime rates were high and the middle-class exodus to the suburbs remained in full swing. We live, however, in a different era, when cities all over the world (including Los Angeles) have redefined themselves, reversing the suburbanizing trend. With that in mind, do we really need, as Hollis writes, "a rallying cry for the reclamation of the city from the grumbles of the skeptical and the stuck-in-the-mud naysayers"? This is hardly an academic question; your response will likely determine how you feel about "Cities Are Good for You." For me, it's a mixed bag, by turns vivid and pedantic, with a discomforting tendency toward boosterism. Hollis - who has written two books about London, where he lives - sees the city as a landscape of limitless possibility that may hold the key to our survival, since we are increasingly "an urban species." He explains: "In 2007 the UN announced that for the first time in human history 50 per cent of the world's population now lives in cities. ... This number is rising at a rate of 180,000 every day; by 2050, it is projected that 75 per cent of the world's populations will live in cities." When Hollis refers to this expanding urban population, he's not talking about the traditional cities of the West. Indeed, he spends much of the book discussing cities such as Shanghai, Singapore and Dubai, which operate according to a different model. His thesis, which he uses these metropolitan models to illustrate, is that "the city is not a rational, ordered place but a complex space that has more in common with natural organisms such as beehives or ant colonies" - complexity theory, in other words, which means that our cities are less inventions than entities, evolving from the ground up, and that the basic unit - the cell, if you will - is the street. Such an argument has its roots in Jane Jacobs' groundbreaking 1961 study "The Death and Life of American Cities." Hollis invokes Jacobs often, citing her contention that "[i]t was the street itself that was the principal object of study, and the metropolis's organizing force." Jacobs was right, of course, as is Hollis about the city as complex mechanism, and when these two related ideas are working, "Cities Are Good for You" begins to sing. Unfortunately, this also highlights a key issue, which is that Hollis spends too little time in the street. His accounts of various cities - Beijing in the days of Marco Polo, New York in the 1960s, contemporary Bangalore with its IT economy - skim over the question of what they feel like, what we might call their quality of life. "The divide between the ambitious dream and the evidence on the ground," he writes of Mumbai, "became clear as soon as I left Bandra station. ... An elevated walkway - the skywalk - rose from the station concourse above the tracks and then continued to direct me along a lengthy covered pathway. From this height it soon became apparent that the walkway was not just avoiding the rail lines but also a squatters' colony that stood only a few yards across a rubbish heap from the busy tracks. Hollis gives a few details about this "no-man's land of the city," but he never does get down in it, preferring to observe from above. This becomes increasingly problematic as "Cities Are Good for You" progresses, cycling through a checklist of urban issues: transportation, walkability, sustainability, inequity, design. It's not that Hollis is uninformed; he knows the territory and is at his best when bringing in unexpected elements, such as the rise of cellphone banking in Africa or the use of social media to mobilize protest movements, to illustrate the connections by which we are now bound. The point, perhaps, is that the Earth is becoming one vast urban matrix. Still, the unanswered question is what it means for the daily life of actual people on the street. That's a contradiction Hollis doesn't seem to recognize. In his view, dynamism trumps all, making the Mumbai slum of Dharavi an expression of "the ingenuity economy, the economy of improvisation and self-reliance" and London's high-tech Silicon Roundabout a reflection of "the same energy and innovation that could be felt amongst the canals and squares of seventeenth-century Amsterdam." It's a bit of a stretch, I think, and it undermines a central issue, which is that such dynamism is not only more fraught than Hollis suggests but also more specific: a function not of cities in general but of each city in particular, developing and evolving in its own way. Cities Are Good for You The Genius of the Metropolis Leo Hollis Bloomsbury Press: 408 pp., $28