The main characters are twins. They enter the 'land of the stories' and throughout their journey, they meet numerous other characters like talking animals and wise old wizards. These twins are central to the story as they are the ones who drive the plot forward by exploring different parts of this magical land and interacting with its inhabitants.
I don't know the exact main characters in this particular book. But in the series, it might be the same ones from the previous books, like the twins who usually go on adventures in the land of stories.
The main characters in 'book 7 land of stories' are probably the twins who have been through many adventures in the previous books. Alongside them, there might be some important fairy - tale characters like the Fairy Godmother or some of the more well - known princes and princesses from different stories. They all play important roles in the events that unfold in this part of the series.