I love all the Valdemar books with the exception, perhaps, of the Arrows trilogy (and I like that series, just not as much as the rest in the series). I hope she keeps exploring this world she's created and highly recommend the Valdemar books to anyone who likes fantasy.

What I currently own from this series:
The Last Herald-Mage: Magic's Pawn, Magic's Promise, Magic's Price
Heralds trilogy: Arrows of the Queen, Arrow's Flight, Arrow's Fall
Mage Winds: Winds of Fate, Winds of Change, Winds of Fury
Mage Storms: Storm Warning, Storm Rising, Storm Breaking
Owlknight trilogy: Owlflight, Owlsight, Owlknight
Vows and Honor: Oathblood, Brightly Burning, Take a Thief, Exile's Honor
singles: By the Sword
Mage Wars: The Black Gryphon, The White Gryphon, The Silver Gryphon

missing from my collection: The Oathbound, Oathbreakers