This is the 3385th most frequent Russian word.
посвященного
"Посвященного" means "initiated" or "dedicated" in English, depending on context.
In this sentence, "посвященного" refers to "dedicated to," describing the novel that is devoted to the heroes.
Этот роман был написан в честь великих достижений, посвященного великим героям.
This novel was written in honor of great achievements, dedicated to great heroes.
Here, "посвященного" is used as a past participle to show the museum that is themed around ancient cultures.
Мы посетили музей, посвященного культуре древних цивилизаций.
We visited a museum dedicated to the culture of ancient civilizations.
In this instance, "посвященного" highlights the month specified for the purpose of promoting reading and education.