This opening chapter introduces the subject matter and objectives of the book. It first explains central terms and provides an overview of the different illiberal trends in Hungary, Poland, the Czech Republic and Slovakia. It then sketches recent conflicts between EU actors and the four East Central European states and explains why these conflicts are of a new quality. Next, it summarises the state of research on illiberal backsliding and on the EU’s tools against it and identifies shortcomings and gaps in the literature. Finally, it outlines the aims as well as the overall structure of the book and provides an overview of the contributions.