Mary Pope Osborne

The magic treehouse whisks Jack and Annie back to the days of deserted islands, secret maps, hidden gold, and nasty pirates.

Eight-year-old Jack and his younger sister Annie use the magic treehouse to travel back to the Middle Ages, where they explore a castle and are helped by a mysterious knight.

Their magic tree house takes Jack and Annie back to the Wild West, where they experience excitement and danger and try to solve a riddle.

Their magic tree house takes Jack and Annie to the Arctic, where a polar bear leads them onto very thin ice.

Guided by a magic rhyme, Jack and Annie travel to ancient Baghdad on a mission to help the Caliph disseminate wisdom to the world.

The magic tree house takes Jack and Annie back in time to feudal Japan where the siblings learn about the ways of the Ninja.

The magic tree house carries Jack and Annie to New York City in 1938 on a mission to rescue a magical unicorn from New York City. They arrive during one of the darkest periods in the city's history--the Great Depression. Even worse, the city is in the grip of a terrible snowstorm. Where will Jack and Annie ever find a unicorn in the city? And who are the mysterious people following them? Includes instructions to make a snow globe.

The magic tree house takes Jack and Annie to Antarctica to search for the fourth secret of happiness for Merlin.

Magically transported to southwest China to find the final object needed to break the spell on the wizard Merlin's beloved penguin, Jack and Annie take a side trip to the world's largest giant panda reserve.

Their magic tree house takes Jack and Annie back to retrieve a lost story in ancient Greece, where they witness the original Olympic games and are surprised to find what girls of the time were not allowed to do.