The Uniting of Europe: Political, Social, and Economic Forces, 1950-1957 (revised edition). By Ernst B. Haas. University of Notre Dame Press, 2004.

The Institutionalization of Europe. Edited by Neil Fligstein, Wayne Sandholtz, and Alec Stone Sweet. Oxford University Press, 2001.

Required reading for anyone interested in the roots of today's EU, Ernst Haas' monumental work, first published in 1958, founded the field of European Union studies. In this sprawling book, Haas lays down the initial premise for functionalism, the idea that establishing policy capacity in one area will likely produce spillover effects in other areas -- with the result being that private and public actors will continue to push for ever greater integration. The founders of the EU themselves appear to have been driven by similar views, intending their creation as a way to lock in peace on a warring continent. Neil Fligstein, Wayne Sandholtz, and Alec Stone Sweet offer a sophisticated, contemporary assessment of the ways such dynamics have played out in dramatic institutional developments across a variety of European policy spheres.

The Choice for Europe: Social Purpose and State Power From Messina to Maastricht. By Andrew Moravcsik. Cornell University Press, 1998.

A modern landmark for the study of the EU, Andrew Moravcsik calls attention not to the subtle, incremental development of the EU described by the functionalists but rather to the forceful role of national governments and their leaders in moving integration forward.  His magisterial overview of the pivotal historical moments of European integration, from its beginnings in 1958 to the Maastricht Treaty, reveals the role of domestic commercial interests in pressuring political elites in key countries to negotiate treaties such as those that established the early common market, later dramatically removed barriers in the Single European Act, and created the euro and EMU. Moravcsik's "intergovernmental" approach provides a crucial complement to the functionalist story, reminding us of the key role that national political leaders have played in the European experiment.

European Identity. Edited by Jeffrey T. Checkel and Peter J. Katzenstein. Cambridge University Press, 2009.

Euroclash: The EU, European Identity, and the Future of Europe. By Neil Fligstein. Oxford University Press, 2008.

Eurostars and Eurocities: Free Movement and Mobility in an Integrating Europe. By Adrian Favell. Blackwell Publishing, 2008.

Figuring out what the EU is can be hard -- but deciding who the Europeans are can be even harder. Early theorists of European integration anticipated a gradual replacement of national political identities with a shared sense of "Europeanness." This has not come to pass. Instead, something more interesting has happened: variations within countries and across social classes, age groups, and professions in the way people perceive themselves and their affinity to Europe.  Jeffrey Checkel and Peter Katzenstein's edited volume provides a nuanced overview of the processes of political identity formation, while Adrian Favell investigates at the ground level how a group of "eurostars" (those professionals taking advantage of the single labor market of the EU to live and work outside their home countries) have a very mixed experience of assimilation. Fligstein's study of the ways in which the benefits of a single European market are unevenly distributed across income groups offers a cautionary tale for enthusiasts of European integration while offering up sociological analysis of the finest order.

The Breaking of Nations: Order and Chaos in the Twenty-First Century. By Robert Cooper. Atlantic Monthly Press, 2004.

The United States of Europe: The New Superpower and the End of American Supremacy. By T. R. Reid. Penguin Press, 2004.

What role does the EU play on the global stage? Is it likely to ever get its act together in the foreign policy realm? The geopolitical stance of the EU and its superpower (non)status is one of the most hotly contested and open-ended areas of concern for EU watchers. Robert Cooper's provocative book lays out one vision for the EU in a broader geopolitical context as a normative postmodern superpower, a powerhouse because of the attractiveness of its liberal, rule-based system of governance (as opposed to a traditional military power like the United States). T. R. Reid's book is a cheerleading tour of the EU during a more sanguine, prefinancial-crisis time, yet its astute observations about the ways in which the EU is exerting its influence in the world are worth paying attention to, just as much as it is instructive to see what Reid's euro optimism has gotten wrong. Both books are written for a broad general audience and make for enjoyable reading.

What Is Wrong With the EU and How to Fix It. By Simon Hix. Polity Press, 2008.

If you can read only one book on this list, make it this one. Simon Hix's crisp and clear diagnosis of the EU's problems focuses, counterintuitively, on the need for more, rather than less, politicization -- but politicization of the right kind. He argues that the EU's ability to undertake needed economic reforms and define its place in the world would be enhanced by clearer contestation between the winners and losers of its policies, allowing for the normal pull and haul of politics rather than the current default to technocratic solutions tempered with frequent deadlock. In addition, bringing more of the EU's decisions into the open would address the widespread apathy and disengagement that Europe's citizens feel about the EU's machinations. Given the astonishing developments of the past 50 years that have propelled the EU to where it is today, and the continued political challenges that are likely to plague it given contemporary economic distress, addressing the EU's shortcomings is a nonnegotiable goal. Hix's book charts a path forward.