Osborne, Mary Pope

"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?."--.

Eight-year-old Jack and his younger sister Annie find a magic treehouse, which whisks them back to an ancient time zone where they see live dinosaurs.

"When the magic tree house returns it whisks Jack and Annie away to the Galapagos Islands where they become World Turtle Experts and must save a tortoise in danger of an erupting volcano"--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.

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.