Such a book or books are said to be "Holy Scripture".
There are different holy books - books considered holy by one religious group or another. Please clarify what specific book you are talking about.
A school operated by a church or religious group is typically considered a religious or parochial school. These schools often incorporate religious teachings and values into their curriculum alongside traditional academics.
buddyas
The founder of the Shakers, as a religious group, was formerly a Quaker. Both Quakers and Shakers use the Bible as their fundamental religious book.
Apocrypha refers to religious texts that are considered to be of doubtful authenticity or not officially accepted as part of the recognized canon of scripture. These texts may offer additional insights or teachings but are not considered authoritative by certain religious traditions.
The biblical canon is the list of books considered to be authoritative. Protestants in particular point to Melito of Sardis, as well as a modernly accepted group of criteria. However, in practice, protestants pull from Jewish canon for the Old Testament, and the Roman Catholic canon for the New Testament.
A religious group can be called a sect. A religious group can also be called a congregation when all attend the same church. A religious group might have more than one sect, or group of individuals, like the Amish.
A religious cult would be considered a group with extreme or deviant beliefs, a charismatic leader who exerts control over its members, and practices that may harm or exploit followers psychologically, socially, or financially.
Another word for religious group could be "faith community" or "religious organization."
AUTHORITATIVE
Principal Based
A big group of books is called a library.I call a group of books a group of books.