When Puck (Kate) Connolly loses her parents and her older brother threatens to move to the mainland, the family house and everything the Connolly's own, including her beloved horse Dove, are at stake. The Scorpio Races award a monetary prize, and Puck enlists to save her family. She's continually harrassed because she's a girl. No one, not even her own family, supports her decision to enter the race. Her choice to race Dove, her own horse, rather than one of the giant water horses, further alienates her.
Meanwhile, Sean Kendrick, 4-time winner of the races, is torn between the control that betting men from the mainland have over the riders (much like the competitive and wealthy backgrounds of modern horse racing) and wanting to help Puck, who he feels kinship with (and maybe more...) having grown up with her on the island.
I listened to the audiobook version which is fantastic. Both narrators -- male and female -- sounded just right for the story. This is a fantasy full of adventure, family loyalty and courage. A really great read.