When you look at your list of books is the list in English? Depending on the language, some books names don't show. I don't know if it has to do with international censoring laws.
Items that are released after mid June 2015 are not translated so the change language trick will no longer work. If you use the JN book checklist feature
(you need an account to see links)
When the book list is produced it now also labels what books your pet will find boring. You can click on those links and see the release date and find out whether or not the change language trick will work without wasting np
Same thing for the gourmet food checklist on JN