This book investigates how the United States and the European Union are redefining federalism to address legitimacy crises in multi-layered democratic systems. Kalypso Nicolaidis and Robert Howse draw upon a collaborative transatlantic dialogue to examine the evolving relationship between various levels of governance. They argue that despite distinct historical and structural origins, both entities are converging toward a shared federal vision for the twenty-first century that transcends traditional debates over devolution and subsidiarity.

Scholars and political analysts frequently cite this work as a significant contribution to the comparative study of federal systems. The text is noted for its high academic density and its ability to bridge the gap between American constitutional theory and European integration studies.