It's not going to be out for another week or so, I thought?

Um. Sasuga Books (https://www.sasugabooks.com/) is, as far as I know, very reliable, and their shipping to the USA is very reasonable. I have no idea what the shipping to Germany would be like, though. Also, they don't have the artbook up for preorder... or vol. 15, so maybe they don't do preorders?