The book is a translation of a book for mathematical leisure widely known to a foreign reader. Its author is a professor of mathematics at the University of Berlin, a brilliant popularizer of science. The book was based on more than 100 essays that E. Behrends published in his column in the newspaper DiWelt. The Russian edition is a translation of the 3rd German edition, which corrected the typos noticed. The book is written in a lively and accessible language, complex mathematical facts are presented from an unexpected angle, while their scientific component is not violated. Numerous historical facts are cited. The book is richly illustrated. The author set out to assure the reader that mathematics is not a dry and tedious subject, but, on the contrary, it is full of charm and admirable. The book is addressed to a wide range of readers, everyone who is ready to occupy their leisure time with exciting and informative reading.