To my knowledge, there isn't a 7th book yet. But you never know, the author could surprise us in the future. Follow their social media or literary blogs for updates.
The 7th book of Land of Stories likely builds on the existing characters and their relationships. It could introduce new challenges for the protagonists. Maybe they have to face a more powerful villain this time or solve a mystery that has been hinted at in the earlier books. It might also explore new parts of the Land of Stories, with different magical elements and strange creatures.
I'm not sure exactly as I haven't read it yet. But generally, it might continue the adventures in the Land of Stories, perhaps with new characters or challenges for the main characters.
Alex and Conner are key characters, no doubt. But there might be new characters introduced in the 4th book who could also be important. For example, a mysterious guide who helps them on their journey. And the characters from the different lands within the Land of Stories world, like the mermaids or the dwarves, could play significant roles depending on the story's plot.
One of the main themes could be adventure. The characters likely embark on new and exciting journeys in this book. Another theme might be friendship as they face challenges together. Also, there could be elements of self - discovery as the characters grow and learn more about themselves throughout the story.