Phew! This book will mess with your head! An epic novel, in the tradition of David Mitchell, it's long, frustrating, confusing, but also exciting, satisfying and quite brilliant. There is also an app, which I don't have, where you can follow many of the individual characters' stories chronologically, rather than in the woven narrative of the book. Apparently, there are 10 different story strands, 3 different interlocking worlds - one of which may or may not actually exist - and many, many characters - one of which seems to exist in two of the worlds simultaneously.
However, it is compellingly readable, and features a dystopian future which is genuinely disturbing.