** spoiler alert ** 
 what if the many worlds interpretation of quantum mechanics was found to be true, and every decision and event spawns a set of new diverging worlds 
 what if macroscopic objects, humans, could travel between these worlds, controlling decoherence through drugs. 
 what if your doppelganger from one of the worlds decided they would much prefer to live your life instead of theirs, they swap, and you need to find your way back to the right world, through many alternatives, to regain what is rightfully yours 
 what if you find your way home and things start to get really weird... 
 Hugh Everett meets Philip K Dick 
 the road less traveled 
 lots of great ideas 
 plot really moves along 
 characters not particularly interesting well developed