Mary Pope Osborne

"Where did the tree house come from? Before Jack and Annie can find out, the mysterious tree house whisks them to the prehistoric past. Now they have to figure out how to get home. Can they do it before dark ... or will they become a dinosaur's dinner?" --

"Jack and his younger sister take a trip in their tree house back to ancient Egypt, where they help a queen's mummy continue her voyage to the Next Life."--

Jack and Annie go back in time to meet Abraham Lincoln himself! They need to get a special feather from him to save Penny the penguin. But President Lincoln is much too busy running a country at war. So the kids go even further back to look for Abe as a boy. Instead, they meet a ragged orphan named Sam who also needs their help. Can Jack and Annie do the right thing - and still save a president, a troubled nation, and Penny as well?

In their magic treehouse, Jack and Annie are again transported to King Arthur's realm, where invisible beings, giant ravens, and mistaken magic spells have a duke's castle in an uproar on Halloween night.

Jack and Annie must travel back in time to New Orleans in 1915 to help a teenaged Louis Armstrong fulfill his destiny and become the "King of Jazz."

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."

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

When the magic tree house whisks Jack and Annie off to Greenland, they're not sure what time they've landed in, but they immediately know what their mission is: save a narwhal! Then they meet a young hunter named Leif Erikson and they ask for his help. But Leif has other ideas...

Their magic tree house takes Jack and Annie deep into the sea, where they meet up with dolphins, sharks, and octopi as they search for the answer to an ancient riddle.

Their magic tree house takes Jack and Annie back to a monastery in medieval Ireland, where they try to retrieve a lost book while being menaced by Viking raiders.