Well, I only received this yesterday as part of the giveaway and have finished it already.
A combination of ill me + ill child + lots of sofa time, but also the fact that I honestly didn't want to put it down.
I was intrigued from page one - gradually being given the details of Nathans circumstances in enough depth to really want to find out exactly WHY he was in that situation. And then the narrative looping back so that we did get the backstory.
I loved her writing style. It reminded me a little of something that Stephen King once said about the process of writing books (tried to find the quote, but gave up!) about how he basically used to re read what he had written and try and get rid of ANY extraneous words, of any padding. It feels like Sally Green has done this and very successfully, too. The writing is pared down - very simple, pure terms and also quite brutal at times (but also peppered with some lovely descriptive passages and imagery).
You get a good sense of the protagonist and gain a huge amount of sympathy for him, without necessarily feeling like you approve of some or all of his actions, in fact quite the opposite. I think that's quite a rare thing, really - so many main 'hero' characters in YA are 'misunderstood but moralistic/self deprecating and noble' blah blah, that it's quite refreshing to read something where the central character is quite amibiguous and you are NOT immediately certain of where the story will end up.
I thought it was great, as you can probably tell 
and I can't wait for the next one to come out (Spring 2015?!)
It's going to be a good one to hold onto for both DCs - I already have a few shelves of Pullman, Wynne-Jones, Susan Cooper etc waiting for them and this one can definitely join the ranks.
Many thanks for my copy :-)