Really solid start to a series -- I can see why people are hooked on these! The world the author lays out is compelling, and the treatment of shifting really appeals to me in a terrible dystopic way: yes, there are horrible downsides to this change, and yes, one of those downsides is the way other people are going to be monstrously freaked out about it. Main characters are easy to root for and the action makes them fly. 
 There were a few points where it felt like a more assertive editor might have helped, catching the occasional paragraph that meandered off-point, but overall this was a really solid read. And I am both looking forward to and worrying about the next one. Success.