There's a bunch of books which recently came out, useful to grasp Henri Lefebvre's legacy in urban studies and theory. Well, in recent times, planning and critical urban studies have been finding again the route for fruitful dialogues and the works of the French filosopher have furnished some of the theoretical concepts useful to underpin radical studies to institutional systems and policy analyses.

Gülçin Erdi-Lelandais's Understanding the City. Henri Lefebvre and Urban Studies(2014, Cambridge Scholars) is briefly reviewed on Ville en Turquie:

Most current research on Henri Lefebvre refers solely to his ideas and their theoretical discussion, without focusing on the empirical transcription of the philosopher. This book fills this gap, and proposes examples about the empirical use of Henri Lefebvre’s sociology from the perspective of different cities and researchers in order to understand the city and its evolutions in the context of neoliberal globalization. The book’s main purpose is to revisit Lefebvre’s still-relevant key concepts to propose new comprehensions of the contemporary city. Case studies in this book will show also that the reception of Lefebvrian concepts differs across different contexts, depending on the social and political circumstances of each country.

Chris Butler's Spatial Politics, Everyday Life and the Right to the City (2013, Routledge):

provides the first serious analysis of the relevance and importance of this significant thinker for the study of law and state power. Introducing Lefebvre to a legal audience, this book identifies the central themes that run through his work, including his unorthodox, humanist approach to Marxist theory, his sociological and methodological contributions to the study of everyday life and his theory of the production of space. These elements of Lefebvre’s thought are explored through detailed investigations of the relationships between law, legal form and processes of abstraction; the spatial dimensions of neoliberal configurations of state power; the political and aesthetic aspects of the administrative ordering of everyday life; and the ‘right to the city’ as the basis for asserting new forms of spatial citizenship.

Stuart Helden's Understanding Henri Lefebvre is a bit older (2004, Continuum) but is crucial for linking Lefebvre to contemporary geography and planning:

analysis of his writings on cities are balanced with those on rural communities, the production of space connected to ideas of time and history, and everyday life linked to the festival and cultural revolution.

Update, April 27. Stuart Elden, on the Environment and Planning D site, update about this Lefebvre's short essay (Dissolving city, planetary metamorphosis), recently translated and in Open Access for the next couple of months. A commentary by David Wachsmuth and Neil Brenner is in OA as well.