Umberto Eco was perhaps the first to draw attention to the phenomenon of an “open work”, in which the “perceiving party” becomes a true co-author. A description of this phenomenon - with many examples from various fields of art and science - is given in the work of the famous Italian scientist, which was considered revolutionary by critics immediately upon its publication. The book is prepared on the basis of the most complete Italian edition, equipped with prefaces by the author, which reveal the reasons for the creation of the work and trace its fate in the European intellectual world.