Another hard book to review. I found how much I liked it changing drastically as I read it, and I suspect I will have to re-read this again to totally make sense of it.
I think my main problem with it really was there wasn't a clear and coherent explanation what the simus are: Mutants? (perhaps, but then apparently engineered ones, but then it's made clear that they appear randomly too. This plot thread is a bit tatty!)? Aliens? The next stage of humanity? Some are telepaths, but what are the others? I don't think I got a really clear picture of what exactly Zach can do that makes him special. (in fact, it's spelled out in the blurb, but I don't feel like I had it explained well in the book itself.) What's clear is they are different, hated, and yet no real reason why. And miscegenation laws again?
Worse I found the characters fairly unlikeable and prone to acting like the feckless teenagers they are. I wanted to smack Laura upside the head more than once, and the only one who seemed likeable was Max.
I did very much enjoy Zach's journey in the ice, but found it very disconnected from the rest of the story.
Anyway. I liked it, but I was left feeling vaguely disconcerted.