I like the NZ/ Australia setting. However it has to be said that most of the time the location setting does not feature as one equestrian school looks much like another.
Issy and her NZ friends find the accents of the Aussies funny, just as we in Ireland do, when they are sent over to the continent for a short stay to participate in team training and a contest. I was a bit surprised by the way this contest is conducted, and how Issie never seems to contact her parents, which for a mid teens girl is odd.
The young people are given school horses of varying abilities and while it makes sense to some that the best riders get the best horses, giving the younger or weaker riders the less skilled horses does seem unfair to them.
We just see training training training so this is not for the reader who wants to read about kids going out for a ride and having an adventure. As the series is about secrets, the secret in the book is a puppy kept quietly in a stable (and none of the people running the stables notices? I don't think).
Lots of info about higher level riding is imparted but the horses are pretty much treated like machines there to work and their personalities don't come through. Issy is given Victory, a schoolmaster. At the end the riders have to compete at a one-day event. Crowds are gathered. Issy's parents are not shown phoning her to wish her luck and tell her to be careful.
The event seems rather too challenging for young riders and I simply cannot agree with riders having to change from showjumping gear and into a back protector and helmet against the clock. The safety gear is obligatory and having something worn loose or wrongly fastened won't help anyone. The rider may also need to adjust stirrup lengths. I believe if the jumping and cross country are run together this way, the clock should be stopped when the rider enters the pit stop area, with let's say a maximum time of three minutes, then that gives time for a correct change of safety gear and the clock starts again as soon as the rider leaves. This is how three-day-events are run after the warmup phases. And why couldn't the jumping be held first and separately, which happens in any one-day-event I've seen. The time appears to be too tight as the riders are shown galloping around a set of fixed jumps. Dangerous, horses flatten at a gallop.
And what is the reason why one side has to jump all their riders first? If a side loses the toss why doesn't their first rider go and then the first from the other team, alternating? It's not cricket. The toss gives far too much advantage to the second team as described by the author. And of course she has to put Issie's team second to go, because the story's tension would deflate otherwise. In a showjumping Nation's Cup (and any Riding Club event here) the teams jump their first riders, then the second riders for each team and so on, sustaining tension right to the final round for all the teams.
One girl calls out helpful directions to the rider who has lost her way. The girl gets praised and the rider gets a clear round. I don't know what rules this is run under, but in showjumping the rider would be eliminated. However perhaps all of this oddness is how Australian riding contests are run.
This is an unbiased review.