Another book about the circle, moreover, about its elementary properties... Is it too bold and is it necessary at all? Indeed, starting with the Euclidean "Beginnings" (300 years BC), the presentation of the theory of the circle both in content and in the choice of ways to prove theorems in countless textbooks of all times and peoples was so exhaustive that it seems that not a single new word can be added here. It would be a mistake to assume that the doctrine of the circle has remained unchanged since Euclidean times and that its presentation in all textbooks is the same. On the contrary, the development of this theory continues in our time.