Sorry to post twice, but I wanted to add some stuff about Princess Academy.
It's hard for me to pick a favorite Shannon Hale book. All three--Goose Girl, Enna Burning, and The Princess Academy--are great. They each have different strengths and weaknesses (though, admittedly, I like them so much I'd be hard-pressed to find weaknesses). That said, Princess Academy reminds me of Holes by Louis Sachar. After I read Holes I declared, "This is a perfect novel." By "perfect" I do not mean that it was the best book I'd ever read (although it is one of my favorites), I meant that it was so tightly written and came together perfectly. Nothing was superflous. Everything had meaning. Everything tied together--there were no loose ends. It was perfectly plotted and perfectly executed. And The Princess Academy is like that.
Princes Academy is MG (middle-grade) instead of YA like her previous two books--the protagonist is 14, so that means it is geared at readers the age of 10-12. And it is also perfectly plotted and executed. Again, as in Holes, everything has meaning. There are no loose ends--the plot is tight. Even the magic system is done right--it arises from the characters and setting and is used correctly to facilitate the plot and resolution without being a deus ex machina. And, like in all her books, the characters are well-drawn. So I highly recommend this book. Read it! Buy it! Support Shannon!