The Kingdom of Fantasty series books tend to be longer and more complicated than the first series. There are more pictures, including maps and puzzles. New fantasy characters often get a two page spread describing them, and even objects in the story occasionally rate a break in the narrative to explain them. There are still the illustrations on every page, as well as the words in different colors and fonts, but these are a bit longer because of the additional information.
The story lines are also more complicated. While the Miceking series has simple plots where Geronimo must go and accomplish one thing, the fantasy plots often have two complimentary story lines as well as more characters. This makes the book a fun choice for more sophisticated readers who might like books like Harry Potter or Nimmo's Charlie Bone but who want a fun read with more pictures.