The most accurate response to the question about how medieval books were related to the process in which they were made is:
Monks in monasteries made the books, so they were usually about religion.
This reflects the fact that the primary source of book production before the printing press were the monasteries, and the content of these books was predominantly religious. The text emphasizes the role of monks in copying manuscripts, indicating that the intellectual and cultural life of Medieval Europe was largely limited to religious topics due to this production process.