Outland by Rhiannon Lassiter
'We have no idea what's behind of any of these Doors,' she said. 'It could be dangerous for us ...and we could be dangerous for it.' The city of Shattershard lies in ruins following a war engineered by three teenagers from Earth. The devastation has left Laura blind, Alex injured, and Zoe without a way home. Forced to leave Shattershard, they're now caught between worlds and face thousands of Doors - with no way of knowing what lies beyond them. And in unknown worlds there are unknown rules. Rules that, when broken, carry a price ...'Lassiter ...is a young writer to look out for' The Times