I have to admit, I fell in love with this author's books and her world of Tortall, which is by no means boring or cliche, despite being a rather traditional fantasy setting.
Alanna wants to become a knight, her twin brother, Thom, doesn't. They switch places, with him going to the temple to study magic and her going to the royal palace to receive training to become a knight. She must disguise herself as a boy, however, because women are forbidden from taking up arms.
This story is not your usual undercover-girl falls in love with the prince, kind of romance, there are several subjects brought up in the story, such as Alanna's problems with hiding her gender through the onset of puberty and dealing with the intrigues at court and unfriendly pages around her.
The first entry in the Song of the Lioness is an amazing read and easy to follow for younger audiences as well, I warmly recommend it.