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.
I'm not sure where I picked up this book; it is from 1939 and incredibly fascinating. Seems to be a collection of ministers who have made contributions but each and every one is special. I've been reading a passage each night before bed. I'm amazed at the consistency of cultural concerns in 1939 compared to 2021.