all cultural events taking place across rio de janeiro city and state are published by the state secretary of culture on this page - easy to use, the menu on the left allow the user to search by date, city, and type of event such as 'literatura' for anything related to books and literature. 

a valuable resource to discover upcoming literary events in rio is the website beco literário, that maintains a detailed agenda on this page.

also useful is the website roteiros  literários, publishing the dates for the main literary events by month across the entire brazil on this link.