The Princess and The Goblin & The Princess and Curdie: George Macdonald

When Princess Irene and her nursemaid stay out too late one night and are chased home by goblins, a young miner boy called Curdie comes to their rescue. So begins a fantastic adventure in which Irene and Curdie must try to stop a goblin invasion, helped by Irene's mysterious great-great-grandmother.
This much-loved tale was a personal favourite of C.S. Lewis and J.R.R. Tolkien. This edition includes the sequel, The Princess and Curdie.