This is reported in the official press release: https://www.unesco.org/ru/articles/yunesko-nazvala-rio-de-zhaneyro-vsemirnoy-stolicey-knigi-na-2025-god

The cities selected by UNESCO as the World Capital of the Book commit themselves to promote literature for all ages and social groups both inside and outside their borders, as well as to organize a program of events for the year.

This year, the World capital of the book is the city of Accra (Republic of Ghana), next year Strasbourg (France) will take over the baton.