I was slightly worried that I would miss Peter Grant as the narrator, but after a couple of pages I forgot about those worries and simply enjoyed getting to know this wonderful new cast of characters and locations (and genii locorum). I really liked Tobi as the new protagonist and was interested to see how differently magic apprenticeships go in Germany. Vanessa Sommer was my favourite new character and I was so excited by her arc in the book and the hints about her future. The mystery was good and I liked that it was set in an area I like very little about, viniculture. 
I liked that the terminology for magic was genuinely different than in the English books, and not simply direct translations of the English terms. The magical history of Germany was also fascinating, if absolutely horrifying. There were so many hints at the historical developments of the magical bureaucracy both in the Nazi period and in the German separation that I would like to learn more about. English magical history is expanding so much in the main series that I would love to explore alternative German magical traditions as well. 
Finally, the little shout-outs and nods to the characters and events of the main series were greatly appreciated and mostly really funny.

2024 reread: I once again had a great time with this book. It was nice to see Tobi and Vanessa again, and I'm so curious to know if Morgane and Kelly are in touch with their London cousins.