I read this book last week and completely forgot to review it; but I enjoyed it.It started out so well, amazingly actually. The parts about a single drop of water being so valuable and that it was a shock to see it wasted really made me think - it was quite thought provoking in that way. I loved the character of Kai and the way he was special; and actually deserved his expensive home etc. I do find that a lot of the rich characters in YA are never explained (their parents jobs, why they live in a big house etc) but this was.
This book has an amazing concept and I can see so many ways it could have gone - seriously; it could have been fantastic. I am sorry to say this though, could have been, at least for me.
The worldbuilding was good, the plot was moving along well and it was so interesting - and then... Kai disappeared. It wasn't as if he was the only main character and the only one that mattered; but he did make up a central part of the plot.
As soon as he left, the others ran after him- and this struck me as way immature. And it ruined the book for me. Up until that point it reminded me of MATCHED (different content, same pace) but then it changed completely and the action just felt wrong.
So I'll have to give it 2/5, but that is only my view - I think if you were looking for a slightly more action packed book out of this, you might have adored it!