Van Rijn notebook

Van Rijn notebook seems to be a pivotal element in the plot of Girl Genius, even though it has only made sporadic appearances so far. It is supposed to contain notes, written Van Rijn himself, on his Muses. By its most recent appearance, it has had additional pages added, presumably by someone other than Van Rijn.

History
Moxana has the notebook hidden in her "cart", and gives it to Agatha, in hopes it can help Agatha make Moxana a new sister. Agatha reads only a little of it (finding it very inspiring) before being distracted by De Boyz visiting her for the first time. The book isn't seen again until after Agatha is kidnapped/detained, when either Moxona or Tinka gets it out of Agatha's wagon and brings it (and themselves) to Tarvek, whom they now recognize as the Storm King; he says he will use it to repair all the Muses. This all happens before Agatha gets the Lu-copy stuck in her head and the resulting battle of Sturmhalten. The book next turns up two and a half years later among the possessions of the Lady Selnikov after her encounter with The Beast. It is claimed that she was a fugitive because she stole a "book and key" from Tweedle or at least his people, but it's made clear nothing we hear about how or why she has it can be trusted. Agatha notes that the book is thicker than before; content been added. Violetta lugs it around until Agatha finally makes time to look at it in Paris.