This book started out promisingly. Five modern-day kids (two sets of cousins) who are used to playing with each other every summer and acting out scenes from a "Secret Country" they've invented are separated for a summer when one set goes to Australia and the other set have to stay with their other cousins. The kids seemed real and engaging to me and I wanted to know what happened next.
What happened next is they found magic swords that can take them through a hedge into--you guessed it--the Secret Country.
And after that the story kind of fell apart for me. It sounds like a fun premise, but the story never really picks a direction. The kids spend most of their time together arguing and telling each other to shut up, and their time apart flailing without trying to communicate with each other.
The Secret Country isn't exactly as they've imagined it, which they remark on repeatedly, but instead of getting organized and trying to figure out what's going on (what the Secret Country is, whether or not it's real, who they're supposed to be in it), they alternately smash things at random and let themselves be carried along by events. It seems to be a throw everything at the wall and see what sticks approach, and it gave me a headache.
The obvious idea, that the Secret Country isn't something they've invented, but rather something that they've discovered, so to speak, isn't even suggested by any of them till near the end of the book. One character keeps back information from the other kids for no apparent reason, again till nearly the end of the book. I hate that.
We're constantly told that the residents of the Secret Country are not what the kids expected, or they look or sound eerily familiar, or they give the kids or each other funny looks. But this happens so often that there's no good way to guess at what it all means.
There are riddles and mysteries, but the reader is not given any power to solve them one step ahead of the characters (in the way of a detective novel), because the answers come from information that the reader hasn't been given yet.
And maybe "answers" is the wrong word, because at the end of the book not one question that's been raised in the story has been answered yet. The author even lampshades this.* Presumably we get some answers in the second or third book of the trilogy, but frankly I'm not all that interested in slogging through a few hundred pages of petty arguments to get there.
*She also lampshaded the character keeping back information for no good reason, and the fact that after going through the events in this book, there's nothing "fun" left for the characters to do. Someone might have to kill someone else to win a war that may or may not be imaginary. I would have an easier time caring about this if the protagonists could decide for themselves what's going on.
Age I'd let Z read it: Meh. 10 or 11.