While the multi-level cooperation of European and national administrative authorities and courts has become subject of numerous jurisprudential studies, the interaction of the European audit institutions has attracted little attention so far. Christoph Thäsler's book fills this gap. Firstly it gives a brief overview of the European budget implementation and budget control. Thereafter it compares the audit authorities of several Member States and discusses the specific problems of external audit in the European multi-level system. It provides a detailed analysis of the legal relations between the European Court of Auditors and the audit institutions of the Member States including legal remedies and the cooperation in European audit organizations. On this basis, the author develops perspectives for a decentralized financial control network and investigates both its legal permissibility and the practical feasibility. He shows, that though a decentralization would be difficult to realize, it is possible in principle.