This book, "Theory of Didactical Situations in Mathematics: Didactique des Mathématiques, 1970–1990," edited by Guy Brousseau and translated by Nicolas Balacheff, Martin Cooper, Rosamund Sutherland, and Virginia Warfield, is a comprehensive exploration of the theory of didactical situations in mathematics education. The book is part of the Mathematics Education Library series, Volume 19, and is managed by A.J. Bishop from Monash University, Melbourne, Australia. The editors' preface highlights the need to make Brousseau's original works more accessible to non-French-speaking audiences, as they have been largely unknown outside of France. The book focuses on Brousseau's work from 1970 to 1990, a period during which he developed the core principles of the Theory of Didactical Situations. The content is structured into several chapters, each addressing different aspects of didactical situations in mathematics. Key topics include the introduction of didactical situations through examples, the foundations and methods of didactique, epistemological obstacles and problems in mathematics, and the teaching of decimal numbers. The book also delves into the didactical contract, the role of teachers and students, and the importance of didactique for teachers. Brousseau's biography provides insight into his early life, education, and career, including his early interest in mathematics and teaching, his involvement in educational reforms, and his contributions to the development of didactique as a scientific discipline. The book is a valuable resource for researchers, educators, and anyone interested in the theory and practice of teaching mathematics.This book, "Theory of Didactical Situations in Mathematics: Didactique des Mathématiques, 1970–1990," edited by Guy Brousseau and translated by Nicolas Balacheff, Martin Cooper, Rosamund Sutherland, and Virginia Warfield, is a comprehensive exploration of the theory of didactical situations in mathematics education. The book is part of the Mathematics Education Library series, Volume 19, and is managed by A.J. Bishop from Monash University, Melbourne, Australia. The editors' preface highlights the need to make Brousseau's original works more accessible to non-French-speaking audiences, as they have been largely unknown outside of France. The book focuses on Brousseau's work from 1970 to 1990, a period during which he developed the core principles of the Theory of Didactical Situations. The content is structured into several chapters, each addressing different aspects of didactical situations in mathematics. Key topics include the introduction of didactical situations through examples, the foundations and methods of didactique, epistemological obstacles and problems in mathematics, and the teaching of decimal numbers. The book also delves into the didactical contract, the role of teachers and students, and the importance of didactique for teachers. Brousseau's biography provides insight into his early life, education, and career, including his early interest in mathematics and teaching, his involvement in educational reforms, and his contributions to the development of didactique as a scientific discipline. The book is a valuable resource for researchers, educators, and anyone interested in the theory and practice of teaching mathematics.