Oh, Parachute, I'm so glad to see that someone else is recommending Mary Stewart's trilogy of Merlin, King Arthur's court Magician! I love those stories, and Ms. Stewart does the Arthurian legends well!
"The Princess Bride" by William Goldman. When a beautiful girl is kidnapped for a forced marriage, her long-abused groom recruits some unlikely allies to go to her rescue.
"Stardust" by Neil Gaiman. A foolish boy promises to bring a falling star to the shallow pretty girl he likes. The star, though, has taken the shape of a beautiful girl, and a powerful witch seeks her, too!
"The Golden Compass" by Phillip Pullman. In a parallel universe, where our souls are external and in the shape of animals, a little girl uses the title artifact to seek the truth. Followed by two sequels, these form "His Dark Material" trilogy.