This was amazing! I'm quickly revising my growing list of books that should be nominated for next year's Hugo, and this one certainly fits the bill. :) 
 The ideas are really awesome. Two big ones, slamming against each other in a truly horrific and out-there way, and all the while, our MC, Faller, falls through the skies on his quest. 
 The book has a parallel structure to it. The present mess and the past slowing catching up to where the present mess began. Revealing the events that made a world that has been broken into city-sized chunks that are repelled from each other as if we were all a part of quantum physics was nearly as fun as jumping and falling from each one of these lands. 
 And what's the other big idea? A virus that wipes everyone's memories. That reveal was pretty amazing, too, as was the epic battle between two old friends, one of whom blames the other for his wife's death and the Faller, who has lost all his memories. 
 Each world-island is just a dystopian present-day world that we know, with no one remembering how to use technology, no power to run things, and not even the ability to read. It feels pretty hopeless, but Faller has the picture of his wife and a map directing him far, far below, through the clouds and islands, to where he might find the answers. Any answers. It's a pretty sweet setup, and the adventure is downright awesome. 
 But how could something like this, the inclusion of a duplication machine, a singularity, and an Earth turned into a macroscopic version of quantum fields actually resolve into a glorious story, rather than a cool premise? Ah, don't worry about that. It does. Rely on the author to walk you through the cool reveals and set us up for one hell of an awesome resolution. :) He pulls it off. 
 I'm really excited for this year's best SF, and this one certainly fits that bill. :) This was really gloriously cool SF. 
 Great concepts, fearless execution and a very solid story with characters that I can't help but love. 
 Woo Hoo!!! :) 
 Thanks to Netgalley for this ARC!