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 expected to fly through this book and find it mostly uninteresting - to my pleasant surprise, that did not happen! I spent probably a good hour getting through all 100+ cities in here. There were a lot of national capitals I was never aware of. It was nice to see pictures of all the cities, as well as learn about their population density and a few fun facts about the location. It actually made me want to see Brussels in Belgium and Prague in the Czech Republic!
I still had to see maps to find where many of the cities were located. But it was great to start & give basic info on the different cities. Many of them I wanted more info &/or more pictures. A great place to start when thinking where you would like to travel!