I agree that it feels like just another chapter break and I think the reason for that is that... how do you say this in any language... the premise (?) of the first adventure
hasn't concluded yet. Like, compared to the Harry Potter-books (because everyone knows about them) the setup is that "Harry goes a year to Hogwartz" and what follows is Preparations for the year, Actual year, and then Returning home. Here the setup was "The crew goes to Denmark to fetch books which then gets sold for large sums of money". While the "large sum of money" was always questionable we still need to actually see them return with the books and attempt to sell them off to Danish scholars or something for this adventure to be concluded.
At... at least that's what I think.
There also isn't really any feeling that "new adventures await (for this crew)", we just know about it because Minna has said so.
(I mean unless you count The Crews' Battle Against the Chef's Food as the next adventure I guess... And I have a feeling we're not gonna see that
)
But I'm very happy for Minna for managing to reach this milestone anyway, and I'm really excited about the next adventure! Bring on all the new ideas for fanfics!