Roman Catholic liturgical books are like big special books that help priests and other church leaders know what prayers to say and what actions to do during different church services.
Imagine that you're putting together a puzzle, but you don't have a picture to look at. The liturgical books are like a picture that shows everyone in the church what the puzzle is supposed to look like when it's finished.
There are different books for different occasions, called liturgical seasons. For example, during Christmas, priests use a special liturgical book called the Roman Missal to help them know what to say during Mass.
There are also special books for saints' feast days, weddings, funerals, and other occasions that are important to the Catholic Church. These books are usually filled with prayers, songs, and instructions on when to stand, sit, or kneel during the service.
Liturgical books are very important to the Catholic Church because they help everyone know what to do and say during Mass and other services. They are like a guide that helps everyone work together to worship God in the right way.