The Magic Tree House series, penned by American writer Mary Pope Osborne, has won several awards for its children's books. The series features two siblings, Jack and Annie, who stumble upon a mystical tree house while chasing a weasel on their way home. The tree house contains books that transport them through time and space. Jack and Annie are entrusted with the mammoth undertaking of retrieving four medallions, each located in a different era and place, to assist a magician named Morgan.