The book "Nonlinear Functional Analysis" by Klaus Deimling is a comprehensive treatise on the subject, covering both elementary and advanced concepts. It begins with an introduction to the topological degree for continuous maps in finite dimensions, followed by discussions on topological degree in infinite dimensions, monotone and accretive operators, implicit functions, fixed point theory, solutions in cones, approximate solutions, multis, extremal problems, and bifurcation. The author aims to provide a survey of the main ideas, concepts, and methods in nonlinear functional analysis, making the content accessible to graduate students with a modest background in functional analysis. The book includes numerous exercises and examples to illustrate the theory and its applications. The structure is organized into ten chapters, each containing sections that delve into specific topics, with concluding remarks and exercises at the end of each section. The book also features a bibliography and an epilogue that reflects on the development of the field and the author's contributions.The book "Nonlinear Functional Analysis" by Klaus Deimling is a comprehensive treatise on the subject, covering both elementary and advanced concepts. It begins with an introduction to the topological degree for continuous maps in finite dimensions, followed by discussions on topological degree in infinite dimensions, monotone and accretive operators, implicit functions, fixed point theory, solutions in cones, approximate solutions, multis, extremal problems, and bifurcation. The author aims to provide a survey of the main ideas, concepts, and methods in nonlinear functional analysis, making the content accessible to graduate students with a modest background in functional analysis. The book includes numerous exercises and examples to illustrate the theory and its applications. The structure is organized into ten chapters, each containing sections that delve into specific topics, with concluding remarks and exercises at the end of each section. The book also features a bibliography and an epilogue that reflects on the development of the field and the author's contributions.