I rather like this book, although some might find the resolution of main problem to be anti-climatic. This book is very character-driven, the main conflict isn't so much between Ri and Seamus's ex Pete as it is between Ri's horse nature and his human nature. Horse-shifters face unique problems even among shifters--all the other types of shifters are predators whereas Ri is a prey animal. Horse-shifters must eat more, they must be vegetarian, and they tend to either run or starve themselves to death. Horses only sleep a few hours a day, contrasting with the many hours wolf and cat shifters (as well as humans) sleep. Horses are creatures of constant movement and constant feeding. Ri is constantly in a state of skittishness, his first instinct toward any threat is to run. This is not cowardice, it is instead a completely normal reaction for a prey animal. The central conflict is between Ri's horse and Ri's human, and Ri has to learn how to balance the needs of both in order to survive.
In the end Ri's human wins, allowing him to confront Pete in a logical, human way. This allows him to diffuse the situation before it results in violence. Some readers may not appreciate how the story is resolved and that's fine, but I really liked the change of pace compared to Skye's other shifter stories (mind, I really liked those too!)
Seamus provides a steadying presence for Ri, accepting his oddities completely even before he found out that Ri was a shifter. He realizes instinctively that Ri needs human socialization, and helps him with that without being patronizing or over-protective. Ri is a fully intelligent adult after all, despite his skittishness.
Pete, Pete is a wolf who had killed his own pack to save Seamus's life. He is very obsessive and slightly unhinged, but ultimately not dangerous to either Ri or Seamus. He believes that he and Seamus are mates and doesn't understand that Seamus is done with him. I actually feel that Seamus may have provided a similar calming presence in Pete's life, which resulted in Pete eventually seeking out a nonviolence solution to get his 'mate' back. Even though it didn't work out for him I think the final solution will be much better for him in the long run.
I have a feeling that we might see Pete again in his own book, and I really hope we do.