These two new books provide strong and timely messages for people concerned with the present and future of cities. Both of them look at the dense, often chaotic conditions of big cities and find solutions where others have seen mostly problems.

Focused on Latin America, McGuirk's book is carefully constructed, striking a balance between reportage and interpretation. A writer and curator who has worked as the design columnist for The Guardian, McGuirk describes what activist architects and politicians are doing to improve informal settlements in cities such as Buenos Aires, Lima, Rio de Janeiro, Caracas, Medell'n, and Bogot'.

While architects and planners in North America and Europe distanced themselves from roles as advocates for social change in recent decades, many of their colleagues in Latin America found ways of addressing the issues of poverty and inequality, says McGuirk. In the north, "the pinnacle of architectural ambition . . . was the museum," he writes, and architects came to see "the museum as a tool of urban regeneration, not to mention urban branding . . ." But in Latin America, a new generation of architects has emerged in the past decade that is engaging with low-income communities and helping them find solutions to their problems.

Looking at his subject from a range of perspectives-socioeconomic, political, and architec-tural-McGuirk tells the stories of people like Alejandro Aravena, the Chilean architect who has initiated social housing projects and gotten residents to help complete them, and Jorge Mario J'uregui, who has worked to improve the quality of housing and public spaces in the favelas of Rio de Janeiro. He ends with a chapter on Tijuana that examines the efforts of people such as Teddy Cruz and Ra'l C'rdenas, who reimagine the border with the U.S. as a future center, rather than an edge.

In Urban Acupuncture, Jaime Lerner, an architect, planner, and former three-term mayor of Curitiba, Brazil, explains how small but smart interventions can make a big difference in cities. As mayor of Curitiba, he pioneered the use of dedicated bus lanes, showing how this humble means of transit could work in much the same way as subways do, but at a fraction of the cost. He casts his eye on places as disparate as San Francisco, Edinburgh, Paris, Moscow, and Tokyo, identifying the things he loves about cities. Pragmatic, idealistic, poetic, and humane, Lerner's book is both a primer and a manifesto on the necessity and indispensability of the metropolis. The author poignantly encourages the reader to save, heal, and love cities.

Jorge L. Hernandez is a professor at the University of Miami School of Architecture and a trustee of the National Trust for Historic Preservation.