George MacDonald 
The Princess and the Goblin [EPUB ebook] 

’The Princess and the Goblin’ is George Mac Donald’s classic children’s tale of fantasy. It’s the story of the young Princess Irene and her good friend Curdie, the son of a miner. Princess Irene finds a secret stairway in the castle and discovers that her great great grandmother lives in a secret chamber at the top of the castle stairs. When Curdie overhears a plot by the Goblins that live beneath the castle to kidnap the Princess and flood the mine he is challenged to foil the plot of the Goblins and save the Princess.