Rated of 5
Wow, wow, wow! Did I mention wow? At first I thought I was going to have trouble with the book, that the moving back and forth in time, between different realities, would be confusing, instead I was absolutely captivated. I let go of trying to track narrative threads and found that it all made sense and didn't at the same time. You should leave the novel a bit turned around, you should leave the novel wondering.
All of the characters are fully realized and vibrant. The narrative is plotted in such a way that regardless of where you are in time, you read anxiously through to the end of each chapter wondering what will happen next, increasingly anxious as the novel progresses because you have become familiar with the characters, the setting, the set-up. It is all both familiar and strange. You have become like Ursula in a way, you know something bad may happen but you don't know what; you feel the sinister atmosphere. Unlike Ursula, you can only watch, not act.
This novel was brilliant.
I should also point out that I read an e-galley, and while I am not always a fan of reading on my electronic devices, I think this actually helped me because I could not easily flip back and forth between sections. I think if I had been able to it would have disrupted much of the narrative"magic" for me. My advice? Read it once through without flipping back and forth. Let the story take you where it wants you to go. If you want to truly puzzle it out, save it for the second reading--because you WILL want to read it again.