Reconstructing Solidarity is a book about unions’ struggles against the expansion of precarious work in Europe, and the implications of these struggles for worker solidarity and institutional change. The authors argue against the ‘dualization’ thesis that unions act primarily to protect labour market insiders at the expense of outsiders, finding instead that most unions attempt to organize and represent precarious workers. They explain differences in union success in terms of how they build, or fail to build, inclusive worker solidarity, in countries or industries with more or less inclusive institutions. Where unions can limit employers’ ability to ‘exit’ from labour market institutions and collective agreements and build solidarity across different groups of workers, this results in a virtuous circle, establishing union control over the labour market. Where they fail to do so, it sets in motion a vicious circle of expanding precarity based on institutional evasion by employers. The book builds its argument on comparative case studies from Belgium, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Italy, Poland, Slovenia, Sweden, and the United Kingdom. Contributors describe the struggles of workers and unions in diverse industries such as local government, music, metalworking, chemicals, meatpacking, and logistics.