The book "Costs and Benefits of Collective Pension Systems" offers a comprehensive analysis of solidarity in collective pension systems. It emerged from a collaboration between leading scholars and practitioners who examine the value transfers within collective pension funds. The authors highlight the quantitative aspects of this institutionalized solidarity and provide insights into the cost differences between pension funds and insurance companies. The discussion on solidarity and mandatory pension systems is particularly relevant, as it has gained importance in recent years. This work is of interest not only to professionals in the pension sector but also to policymakers and researchers dealing with the challenges and opportunities of collective pension systems.