Mary Pope Osborne

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

"Travel to Ancient Greece with Jack and Annie as they meet Alexander the Great and help tame his wild stallion"-- Provided by publisher.

The magic tree house takes Jack and Annie to an African rainforest, where the siblings encounter gorillas and learn to communicate with them.

Set in Ireland, Jack and Annie meet an Irish girl and go on a magical adventure that changes the girls lifeshe grows up to be Lady Gregory, who helped bring back the Irish legends, started a theater, and helped the Irish people regain both their heritage and their pride.

When eight-year-old Jack and his seven-year-old sister, Annie, join a group of nineteenth-century explorers aboard the H.M.S. Challenger, they learn about the ocean, solve the mystery of its fabled sea monster, and gain compassion for their fellow creatures.

Jack and Annie travel back to Victorian London when Merlin asks them to use their magic to inspire Charles Dickens to write "A Christmas Carol."

Having used their magic tree house to travel to India, where they must get a gift to help free the dog Teddy from a spell, Jack and Annie have adventures involving a tiger and other endangered jungle animals.

When the magic tree house whisks Jack and Annie away to Australia, they go up against a wildfire! And they're not alone. Jack and Annie must help a baby kangaroo and a koala escape from a fire-filled forest. Will they be able to rescue the animals in time?

Jack and Annie are transported by their magic tree house to the time of the Civil War where they meet Clara Barton.

The magic tree house takes Jack and his sister Annie to the Great Plains where they learn about the life of the Lakota Indians.