Worth a look
One thing I've always appreciated about Tamora Pierce is that regardless of how predictable a plot may (or may not) be, the journey there is always enjoyable and worth reading. Therefore, even though I found "Sandry's Book" a little less engaging than her entries in the Tortall universe, I still would recommend it to young readers. Maybe she intended the Magic Circle universe to skew younger than her Tortall one. It's hard to say, as I have not yet read the others. At any rate, she takes the time to give each character a unique voice, and her writing is, as always, clear and comfortable.