One of my favorite writers for tween and teen agers is
Tamora Pierce. She writes books set in
a world where magic is possible, tells very interesting & adventurous tales
(her books are entirely suitable for adults too), and peoples them with
believable characters … particularly with girls & women who are fully
realized and not pigeonholed into roles.
Overall any of her books has much to recommend it. She tends to write in cycles of three or
four where some peripheral character in one series will become the central
character in another. Anyway, in Battle Magic we pick
up the adventures of Briar, Rosethone, and Evvy as they cope with war between
(their world’s analogs of) Tibet and China.
You don’t need to have read the previous books featuring these
characters to enjoy this book.