The Door in the Sky

"Come back here at midnight, Ricky."

Eleven-year-old Ricky Austin watches in stunned silence as those words magically appear in the stars during a show at the Chicago Space Museum. But why can't anyone else see the message? Any why must he bring Jello?
His teenage sister, Allie, follows him back to the theater at midnight. They're both whisked through a door in the sky to the kingdom of Galdoren, where they quickly befriend a mischievous star and make a powerful enemy of Queen Glacidia, a one-eyed witch who rules over a land of never-ending winter.
On their quest to reach a castle riddled with secrets, this bickering brother and sister will encounter a magic carpet with a terrible sense of direction, invisible knights, a cowardly dragon, a demonic shadow, and a candy farm filled with exploding Red Hots.
Will that scruffy teen alchemist, Henry, be able to master his spell book in time to help the siblings? And will ricky ever get the hang of flying, or will he forever be banging his head against the light fixtures?