The Princess and the Goblin.
This is a really wonderful book written by George Mac Donald, the contemporary and inspiration of C.S.Lewis.
It is written for children of younger ages, but I, as a teenager, found it very interesting and well written.
It had a really great theme of faith.
It's a quick and easy read, and I suggest you look into it.
Here is a synopsis(of sorts).
Princess Irene lives in a
castle in a wild and lonely mountainous region. One day she discovers a
steep and winding stairway leading to a bewildering labyrinth of unused
passages with closed doors - and a further stairway. What lies at the
top? Can the ring the princess is given protect her against the lurking
menace of the goblins from under the mountain? This complete an
unabridged edition of "The Princess and the Goblin" is an ageless story
of magic and mystery.
Just take a look into it when you get a chance.
It's appropriate for all ages.