This is a list of all of Tamora Pierce's books and series, in publication (and for the most part, in chronological order). For a person who is a stickler for reading series and books in order, this will be extremely helpful to you. I have been a fan of this great author for many years now, and her books remain in my mind the ideal fantasy books.
Her first series is the Song of the Lioness Quartet, which tells the story of Alanna, and her journey to become a knight. The books are as follows; Alanna: The First Adventure, In the Hand of the Goddess, The Woman WHo Rides Like A Man, and Lioness Rampant.
The next series set in Tortall is The Immotals Quartet, and tells the story of Daine, a young mage who arrives at the royal palace of Tortall a few years after the conclusion of the Song of the Lioness Quartet. It follows her adventures as she explores her strange powers. The books are; Wild Magic, Wolf-speaker, The Emperor's Mage, The Realms of the Gods.
The Protector of the Small Quartet is the story of Kel, and how she strives to become a knight like her heroine Alanna in the midst of her war torn county. The books are; First Test, Page, Squire, and Lady Knight.
This next series contains only two books, but they are much longer and intricate. They are in my opinion, Pierce's best so far, and tell Aly's story, the daughter of Alanna. The books are; Trickster's Choice and Trickster's Queen.
And now this latest series set in Tortall takes us back in time, 200 years before Alanna's series. While it is not necessary to have read the previous books to understand and enjoy the Legend of Beka Cooper books, I personally would reccomend it. There will be three books in the Beka Cooper series, Terrier, Bloodhound, and Mastiff!
I hope this helps, and that you will enjoy Ms. Pierce's Tortall books as much I have and still do! She's a splendid author, and I can't wait to see what she'll give us in the future! Also, be sure to check out her fantasy books for younger readers.