The book reviews monetary applications of overlapping gene- rations models and models with cash-in-advance constraints. It focuses on the implications for monetary economics. It tries to make sense of the available indeterminancy propositions. They are the most puzzling property of OGMs. The book surveys and synthesizes most of the available research papers. Assesses the usefulness of the approach for the advancement of monetary economics. The book can be used as a non-technical introductory text, which relies foremost on intuitive arguments.