It took me about 2 weeks to read this- not solid reading owing to work commitments - but enough compulsion to continue to encourage me to complete reading it.
I felt it started very much in a Harry Potter type of way with the children at boarding school, but there the similarity ended and the boarding school was a tyrannical unpleasant place to be, including its isolated cell the Sky with its meaningful painting to give hope to all who may be interred there, the teachers and staff sounded so harsh, so it was no wonder the children wanted and then managed, to escape.
The narrative style is descriptive and brings fantasy and reality together, I was well able to imagine the characters in my head: the dog-men - lurking in the shadows and waiting to be given the orders to search and pounce; the Phalange a type of underworld gangster mob and Consolers, motherly and kindly the sort you want to curl up with! The four heroes were likeable two "jolly good chaps" and two charming attractive girls; and the sort that younger readers might wish to identify with. Their paths cross in a chance way and then their future destiny evolves at a swift pace taking them away from school into the mountains then to a city where they become involved with the fight for freedom.
I did feel that parts of the story were a little rushed and perhaps lacked depth: like the freedom rebellion but then I remembered that this was meant for young adult readers (which I certainly am not at my age!) so trying to think of it from that age group perhaps too much description might `lose' and / or confuse the readership?
The story also touched on young love, life and tenderness and also death which I did find quite surpised and saddened me, but it was nice that it wasn't all sweet and happy after the revolution.
I would say that it would certainly appeal to older teens and young adults.