Day of the Dragon King (Magic Tree House 14) by Mary Pope Osborne, Scholastic Books 1998,
Book in near Mint condition, Stories for young readers.
For this adventure, Jack and Annie are in Ancient China!
When the tree house lands in ancient China, Jack and Annie are told to beware the fearsome emperor . . . It's not long before they learn the warning is right!
In search of an old Chinese legend, they head to the palace of the dragon king. But he is not pleased to see them! And when they find themselves lost in his spooky burial grounds, only magic will help Jack and Annie escape!