Jack and Annie travel 500 years back in time to Florence, Italy, and spend a day helping Leonardo da Vinci in the hope of learning another secret of happiness.

"When a mysterious note invites them to Camelot, Jack and Annie travel in the magic tree house to the magical kingdom where they must find a lost dragon"--

A collection of well-known tales from medieval Europe, including "Beowulf," "The Sword in the Stone," "The Song of Roland," and "Gudren and the Island of the Lost Children."

"Jack and Annie travel back in time to 1925 Nome, Alaska, where they meet Balto, the famous sled dog, and help save the town from illness"--

"The magic tree house whisks Jack and Annie to Africa where they must use magic to save a rhino and her baby from poachers"--

"Jack and Annie travel in the magic tree house to Galveston, Texas on September 8, 1900-- the day of the worst natural disaster in US history"--

This ebook collection includes Dolphins at Daybreak (#9), Ghost Town at Sundown (#10), Lions at Lunchtime (#11), and Polar Bears Past Bedtime (#12).
This time Morgan le Fay, the magical librarian of Camelot, challenges Jack and Annie to find the answers to four riddles. To do so, they must travel under the sea and to the Wild West, the African plains, and the frozen Arctic. It’s a difficult and dangerous task,

...

"When Jack and Annie came back from their adventure in Magic Tree House #53: 'Shadow of the Shark,' they had lots of questions. How many teeth do sharks have? What is their favorite food? What are some other top predators? How do they keep life in balance? Find out the answers to these questions and more as Jack and Annie track the facts about sharks and other predators"--

"Jack and Annie use the magic tree house to travel back in time to 1947 Brooklyn, New York, where they pretend to be batboys at Jackie Robinson's first game with the Brooklyn Dodgers against the Boston Braves"--