Princess Ben by Catherine Gilbert Murdock
Not your typical fairy tale.
When Benevolence’s parents are assassinated, she becomes next in line to the throne. Manners and ladylike behavior become important as Ben comes under the notice of her manipulative aunt, Queen Sophia. Ben stubbornly refuses to conform, and is locked in the castle’s tallest tower where her aunt hopes that hunger and loneliness will break her spirit. However, Ben stumbles upon a secret enchanted room, where she begins her study of the magic arts. With her newfound freedom and secret knowledge, she learns to find the strength she will need to save her kingdom.