The first thing Nate noticed were the maps. They covered the walls like wallpaper. There were maps of the world, some bigger than he was, and maps of oceans and continents and places Nate had never heard of. There was even a map of the moon and the stars.
Flight of the Phoenix by R. L. LaFevers
Middle Grade Carousel 
This book sounds fun! Thanks for sharing about it!
It’s a very sweet lower MG adventure. We both enjoyed it a lot!