There was definitely a choice made by the author in this novel that was a terrible idea. For the sake of spoilers, I will not tell you what happens, but a hint would be this sentiment we all seem to share. We all seem to hate when a favorite primary character is practically completely removed from the majority of the of the story. When this event occurred, I was both confused and angry to a degree. I almost threw the book.
The positive sides of this novel would definitely be the kick-butt-ness of the main character that was present in the previous book Greta and the Goblin King. In addition, the plot twist that occures in the novels was very unexpected and riveting. I give Greta and the Glass Kingdom THREE STARS OUT OF FIVE!