Talia, a young girl of thirteen, dreams of becoming a Herald, and doing great deeds. There is one slight problem. Talia is Holderkin, a group of people living on the border of Valdemar that keep to themselves and have a very strict view of a woman's place. On the day of her thirteenth birthday, she runs away from the Hold, and the looming threat of becoming a First Wife or an Underwife. On the road she meets (slides down the hill in front of) Rolan, a 'runaway' companion. That meeting changes her life forever. 
 This is the first book of a trilogy that is a good introduction to the Valdemar series, and it provides a majority of the background you need to understand the Heraldic Gifts, the Companions, and the role of the Heralds. There is not a lot of action; this book is mainly used to set-up the world and introduce the characters that will be reappearing through out the following books (this trilogy & beyond). 
 I really, REALLY like this trilogy! Arrows of the Queen was the first book I read of Mercedes Lackey, and the book that has had me reading ever since.