I'm still in the middle of Winds of Change and I think that I finally figured out why I like her Valdemar books so much more than most of her other books. It's a fantasy story that manage to carry a plot line that fits for adults without going into extremes. Most fantasy seems to be directed at young adults, which shows in both the strength of the plot and the language. Some fantasy is too far in the adult realm; J. R. R. Martin or Terry Goodkind both of which seems to take pleasure in trying to shock the reader. Misty seems to manage to be in between. The plot certainly contains adult elements and deals with many issues that most fantasy ignore (adult relationships, torture, love, single sex relationships, female heroines, the evil that lurks in the heart of man, etc).
Somehow, it's a more real world than most others, and it's not perfect, which makes it a much more believable world. Bad Things can happen to good people, and quiet retirement in the country with 6.7 kids is not guaranteed if you are a hero.