I think this is a decently compelling story that is held so strongly back by its structure. It took me half the book to really have things start to click for me. After that point, the main characters were both sympathetic and completely unlikable in a way that made them and their story very compelling. The relationship between the two sisters, and between their entire family is a highlight. 

As many other people have already said, the narrative bounces between plot threads and timelines, which I did not think was so confusing for me as it was jarring. For the first half of the book, it really only broke the momentum of the story, making me bored and slogging through chapters. My favorite parts of the book are when we get a few chapters following the same story thread and can really start getting invested in one version of the characters (which leads to me becoming interested in the other versions of the characters throughout the different timelines). I've seen a review speak about how this structure mirrors the non-linear timeline of memories of trauma, and while I can see that, this thematic structuring does more harm than good in the execution. It is better done in the second half, after I had some connection to what was going on without interruption.