The increase—or enlargement—in the membership of the European Union from 15 to 25 countries is historic for a number of reasons. The most obvious is, of course, the joining of the former communist countries with the West, the symbolic and real ending of the division of Europe. Beyond the head-line-grabbing news stories, though, there are many other implications of this most recent expansion of the European Union. The books under review, both in Routledge's Advances in European Politics series, concern themselves with two distinct consequences of this enlargement. Widening the European Union, edited by Bernard Steunenberg, is primarily concerned with explaining the institutional reforms of the Union necessitated by Eastern enlargement. Europe Unbound, on the other hand, edited by Jan Zielonka, is interested in the issue of boundaries, both the new boundaries of the EU as of 2004, and those in the future, as the question of where Europe's ultimate boundaries lie is an affiliated issue in this volume. Taken together, both of these books present a good picture of the state of European integration studies at the moment, a state of affairs quite a bit different from the first several decades of European integration scholarship. The Steunenberg volume adopts a unified approach to the study of EU institutional change, that is, institutional rational choice. The Zielonka volume, by contrast, includes a diversity of approaches, from historical to theoretical, some descriptive and some with a wealth of empirical detail.

Anyone familiar with the research perspective of the journal European Union Politics will recognize the theoretical underpinnings of the articles included in Widening the European Union. Indeed, the justification for adopting an institutional rational choice approach to the relationship between institutional reform and enlargement is the finding that previous work on enlargement suffers from the inability to engage in comparative analysis. This is “partly due to the strong emphasis on case study research in this field and the lack of a clear theoretical orientation” (p. 9). The present volume, then, is to serve as a sort of corrective to this problem, as it represents “theory-driven analyses of the institutional consequences of the Union's wish for enlargement… [whose] analytical framework allows us to analyse and explain the process and outcomes of decision-making, which are taken as the result of the interactions between political actors within the context of a specific set of institutions” (p. 9).

After a chapter by Keith Dowding that provides an overview of current rational choice theories on institutional change, and in particular with reference to the European Parliament, the Commission, and the European Court of Justice—a chapter that would serve very well as introductory literature to this topic—the book is organized into three sections. The first section, Constitutional Aspects of Enlargement, includes four chapters that deal with, in turn, the costs and benefits of enlargement based on the EU's mix of federal and confederal institutional structures, with specific discussion of citizenship rights; a discussion of the enforcement costs of enlargement and the utilization of an analytical framework provided by the economic theory of optimum legal areas; a theoretical assessment of several accession scenarios on the EU's effectiveness and member states' efficacy; and the impact of enlargement on EU decision making, with specific reference to the use of different voting procedures and their relationship to the number of member states and their preferences. The second part, Reforming European Union Decision-Making, is made up of three chapters focusing on reforms to the Council of Ministers, the EU's budgetary decision-making process, and the European Central Bank. These chapters argue for changes based upon probable effects of the enlargement. Finally, the last section, Dynamics of Widening, includes three chapters that treat the issues of the relationship between widening and deepening the Union, based upon modeling integration negotiations; the role of parties, in particular, party groups in the European Parliament as agents of the integration process; and thoughts on a new constitution for the EU, elaborated with the help of constitutional economics.

Europe Unbound is a quite different book than Widening. While there is not a unified methodological approach as in the former, the twelve chapters range from historical and normative to theoretical and empirically based, and in so doing cover quite a bit of territory. In addition, disciplines other than political science are represented, including history and sociology. In short, the subtitle of the book gives a good clue as to the general subject of the book, that is, how the changing boundaries of the EU, in particular the current enlargement, will alter or redefine the EU. In covering the issue of boundaries, the chapters approach the topic in a variety of ways. For example, Where Does Europe End? raises the question of reimagining the definition of boundaries, and of the EU itself. Perhaps a multilevel polity requires less defined boundaries than do (did) nation-states? What about transnational activities, such as crime, and the attendant response of police forces working together across borders? These are some of the big questions that are tackled in this book, and through the variety of analyses, the picture that emerges is a bit different than what has been the “official” EU and received notion of what will be the consequences of this enlargement. Put simply, the reality will be much more complex than any simple vision of democratically stable and economically developed and prosperous countries coming about after a relatively brief transition period, with the continual enlargement eastward only ending at the geographic limits of “Europe.” Rather, a Union might not be constrained by geography, the presence of more ethnic minorities within the Union may necessitate the formation of an EU “internal” minorities policy, transnational migration may result in different classification of non-EU peoples, and so forth. This Eastern enlargement, in other words, may change the very nature of the EU in the future.

Taken together, what do these two books provide or add to the existing literature on European integration? Both, I think, achieve what they set out to do, namely, in the case of Widening, to bring EU institutional change instigated by the current enlargement under the analytical lens of institutional rational choice, and therein provide insights derived from this theoretical framework; and with Europe Unbound, to convey a sense of the historic nature of the current enlargement beyond the obvious fact of the recent political history of many of the new members, and instead focus on the multi-faceted nature of the EU's soon-to-be new eastern borders, both at the border and with the changes this implies for such policies as Justice and Home Affairs (JHA) and security. From a reading of Widening, one certainly appreciates how new voting rules in the Council, arrived at in the Nice Treaty, may affect the development of new majorities in the decision-making process, or the case for introducing regional representation in the Economic and Monetary Union (EMU). Europe Unbound forces one to think of the consequences of the EU's new external borders on its new internal borders, that is, internal boundaries semidissolving within the integrationist dynamic, and the implications for internal migration and security issues, such as illegal migration, drug and modern slave trafficking, and so forth.

If Widening focuses one's attention on institutional reforms and their consequences for EU decision making, Europe Unbound introduces a different perspective on the future identity of the EU. Both books ask different questions and stimulate thinking on their respective answers, but put together, they testify to the enormity of the task at this particular stage in the history of European integration. Both books are sobering reminders of the fundamental challenges this current enlargement represents for Europe.