Books can be attributed to "Unknown" when the author or editor (as applicable) is not known and cannot be discovered. If at all possible, list at least one actual author or editor for a book instead of using "Unknown".
Books whose authorship is purposefully withheld should be attributed instead to Anonymous.
This is an excellent book I bought some years ago. It illustrates the methods and expertise of the monastic illustrator.
In a world lit only by candlelight, these talented artists worked for years to complete hand illuminated prayer books, Bibles, documents, and Liturgical sheet music.
Of course, these works would only be affordable at the time to royalty and very wealthy nobility. Many of the manuscripts were kept in the monastery libraries as canonical treasures.
The book is plentiful with the beautiful detailed breathtaking examples of the work and corresponding explanations.
The only thing I would have liked to have seen is more colored plates than what was offered.
There were so many examples of these masterpieces, I could only assume the cost would be prohibitive to make the book affordable to a wide audience.