‘Strangely, American federalism has been largely absent from American political development (APD) scholarship. Jared Sonnicksen’s insightful, stimulating and ambitious book represents a significant contribution to fill this gap. Building on the concept of immanent fragmentation as an institutional reality and regulative idea, this innovative account of American federal democracy "in" and "through" time has a lot to offer, for students of American politics and comparative federalism alike.’Jörg Broschek, Associate Professor and Canada Research Chair in Comparative Federalism and Multilevel Governance, Wilfrid Laurier University, Canada