I felt like this series was made with me in mind, but I realize of course that it is also targeted at young adults and teenagers. I was a teenager in the 90s and had a frenzied Wolfgang Holbein phase where I read many of his most popular books. "Der Greif" was one of the most popular and one of the best.
I was a huge fan as a teenager. I also bought the audio play version as a young adult. I realized when I got older, that Holbein has many faults (mostly repetitions of language patterns and plots/characters, lots of clichés and he got his ideas from other famous authors I didn't know as a teen). But "Der Greif" as a live action show is a dream come true for my inner teenager none the less. It's amazing to see the world they came up with, and I really like how they did it.
They did an incredible job overall with a few weak elements that I can forgive easily. The changes and additions they made are reasonable and well done. I don't care for fantasy or teen drama, but I found the characters sympathetic and the drama engaging. That alone is rare for shows from this genre.
I think I could see the influences from "Stranger Things" and "Dark", but they did it very well.
If you like me were a teenager in Germany in the 90's, you will find they have you in mind (especially in the first episode) and lots of music is referred to in almost every episode. The main character is making mix-tapes for his love interest. It almost gets a bit too much, but doesn't take away from the overall story.
I will definitely watch the second season and I also think you don't need to have read the book to "get" what is going on. To be honest, the story of the book is rather weak, it is more about atmosphere and teenage angst stuff. The story in the show is interesting enough, they made it look really great and have nice character building and good drama. A good pace and some action.