Concept:
The World Book Capital is an international designation awarded annually by a specialized United Nations agency to acknowledge a city's commitment to promoting books, literacy, and reading culture for a duration of one year starting from World Book and Copyright Day (23rd April).
Step 1:
The United Nations Educational, Scientific and Cultural Organization (UNESCO) manages this global program along with major advisory committees representing publishers, booksellers, and libraries.
Step 2:
Looking at other options: WHO deals with global public health, UNHCR deals with refugees, and WIPO handles intellectual property framework. Therefore, UNESCO is the correct body responsible for cultural and literacy initiatives.