In the "Classifications" tab in a book edit page (such as https://circulation.librarysimplified.org/admin/web/collection/NYNYPL%2Fgroups/book/NYNYPL%2FBibliotheca%2520ID%2Fktdezr9/tab/classifications),  a book's Audience and Fiction Classification will default to "Adult" and "Fiction" respectively, even if the book doesn't have those values set. The UI will default to those values but they are not actually set until the admin saves the changes. It turns out that the book won't actually have those values set.

Fix: for books that do not already have an "Audience" or "Fiction Classification" status, have a default value to make it clear that there is no value. If an admin tries to save without any values set, display a warning message.