Off the Rails — Tae Keller

Mihi and her friends are heading back to the Rainbow Realm—and this time, they have to save the princess.Mihi, Reese, and Savannah thought their fairy tale realm adventures were over. But just as they were getting ready to go home, they learn that their first friend in the realm, Princess Pat, has disappeared on a quest of her own. Pat is traveling around the fairy world trying to gather enough magic to save the Rainbow Realm, but the journey is too dangerous, and Mihi, Reese, and Savannah are the only ones that can save her.But as the girls chase after Princess Pat, they meet creatures and learn stories they've never heard of before, from cultures all over the world. And slowly, they realize Princess Pat might be the problem. Can they save the fairy tale world from their friend's destructive quest?