What does the page for each level show?

The level's stars (when "Difficulty stars" is on), its name and the mazes it holds, for example "Mazes 21 to 40". You can give each level a name of your own in the boxes under "A page for each level" (or let the AI draft them); the page then shows your name, with the level under it. A book of only one level has no level pages.