Entertaining! It's not a complex mystery, but it's interesting enough to keep me well entertained for 16-1/2 hours (the length of the audio version). The plot twists from one view to another, and even though I was pretty sure I'd picked out at least one or two of the troublemakers, I was never totally sure until the end. This is the only one of this series that I have read (listened to), but I wouldn't hesitate to pick another if it becomes available as a daily deal with an inexpensive audio version to go along with it.
The primary characters were appealing to me ... nice, decent, ordinary people, people I might like to meet. Having traveled to many places in Germany, I could feel the atmosphere there. I would like to have visited the (presumably fictionalized) location of this story. On the other hand, maybe I did and didn't know it! Germany is full of these wonderful, scenic sites. There are a few sad and scary scenes, but most of all, it's just a good mystery.