When Milo's uncle and Tilly's grandfather are poisoned by a mysterious copy of The Wizard of Oz and fall into a deep sleep, Milo and Tilly travel to the Emard City to find out who is behind the poisoning.

"The Joneses have just won the Great Montgomery Book Emporium in a contest, and it's every book lover's dream! The pull of a lever calls forth a room full of marvelous wonders--from the Room of Woodland tales with its squirrels and mice, to the rocket ship in the Room of Space Adventures, and the aquarium ceiling in the Room of Ocean Tales. But there is more to the Emporium than its thousands of books in extravagant displays. In fact, the previous...

Eleven-year-old Tilly Pages, who has found comfort in her grandparents' bookshop since her mother's disappearance, now learns that she can bookwander into stories, and decides to seek her mother.

Tilly Pages and her friend Oskar journey to Washington, D.C., where she wanders inside the books at the Library of Congress and they try to stop a nefarious plan with some powerful help.