" The law of unjust enrichment is of central importance for all areas of civil law - and beyond, if we consider the repercussions on reimbursement claims under public law. Complex issues such as intricate triangular transactions as well as the uncertain content of a claim of unjustified enrichment are systematically and clearly explained. Where appropriate, the author develops new and balanced solutions. New rulings and important publications are extensively analysed in the relevant context. "