I'm going to be critical of this in a way that might seem to some to be unfair/unwarranted.
The story was cute. Nancy Drew was one of my favorite spunky girl characters when I was growing up. In many ways, she was a welcome, forward addition to her genre before this most recent renaissance of children/YA fiction.
That being said, this graphic novel addition was disappointing. I jumped into the middle of the story. This was the second of a trilogy, but as others have noted, this could have stood alone with some tweaks to the initial premise.
I think, overall, I just expected more from this than I got. All of the characters are white. Additionally, Nancy has these throwaway lines that are so regressive (e.g., Male character: "Why are you so nosy?" Nancy: "I'm a girl detective!" Why couldn't she just have said, "I'm a detective!")
I'm a believer that children's lit strongly shapes our imaginations. I realized recently how much I automatically assume characters (when minimal description is given) are white. That's largely because of what I read as a kid. There are so many subtle ways that children's lit shapes our imaginations. This Nancy Drew novel was disappointing because of what it could have done, especially in its graphic novel form, and the little subtle things that the authors chose to do. I believe they can do better.