^[a] Fair use media is excluded when the book is ordered. This is not necessarily a problem. Just make sure that the absence of this content does not cause a problem with the text, such as "As seen in the above [fair use] picture, ...". Consider replacing them with free media from Wikimedia Commons if possible.
^[b] This is not an assessment of the quality of the book as a whole, but rather a rough estimate of the average quality of the articles therein. Books with high averages may be missing content or suffer other problems. Conversely, books with low averages may contain articles with outdated assessments, or articles which may never grow beyond a certain limit simply because there is not a lot to say about them.