This two-volume book, published open access, brings together leading scholars of constitutional law from twenty-nine European countries to revisit the role of national constitutions at a time when decision-making has increasingly shifted to the European and transnational level. It offers important insights into three areas. First, it explores how constitutions reflect the transfer of powers from domestic to European and global institutions. Secondly, it revisits substantive constitutional values, such as the protection of constitutional rights, the rule of law, democratic participation and constitutional review, along with constitutional court judgments that tackle the protection of these rights and values in the transnational context, e.g. with regard to the Data Retention Directive, the European Arrest Warrant, the ESM Treaty, and EU and IMF austerity measures. The responsiveness of the ECJ regarding the above rights and values, along with the standard of protection, is also assessed. Thirdly, challenges in the context of global governance in relation to judicial review, democratic control and accountability are examined. On a broader level, the contributors were also invited to reflect on what has increasingly been described as the erosion or ‘twilight’ of constitutionalism, or a shift to a thin version of the rule of law, democracy and judicial review in the context of Europeanisation and globalisation processes.