This is actually my favourite book in the series so far. Here is why:
1. The horse scenes and moves are more realistic in this book than in the first two. They discuss actual dressage movements and test sections, and grading, rather than just flying over jumps. Half- pass, shoulder in... And the author actually explains the basics of the movements in the book, but not in an overly educational, ram it down your throat way.
2. You actually start to see some character development and see why the characters act the way they do in this book. Take Brooke being Carly's cousin. Prime example.
3. There are some true "lightbulb" moments in the book, where you and the characters make realizations at the same time. That's kind of cool, because not many authors can write like that.
Sure, the book is still written for the 10-12 year old mindset. Sure, the books are light in theme and extremely easy reads. But they are enjoyable, and if you love horses, this series is highly recommended.