"Cosi Fan Tutti" is a famous opera by Wolfgang Amadeus Mozart, written in 1790 with an Italian libretto by Lorenzo da Ponte. The plot of the book is imbued with intrigue, love intrigues and comic situations. In the book, we encounter two pairs of lovers who test their loyalty to their partners. To test the girls' loyalty, their husbands come up with a cunning plan to determine how loyal the girls are to them. This leads to many comical situations and unexpected developments. "Cosi Fan Tutti" is not only a deep study of love relationships, but also a masterful portrayal of morality and frankness in relationships between people. Each character finds himself in unique situations, which makes this book exciting and interesting for readers of all ages.