It's weird to read what's essentially official/sanctioned fanfiction and in the end, all I could think was that I've read so many better fanfics. There was nothing wrong with this book and I do think the plot, plus the whole idea of quantum entanglement, was pretty awesome. But it just lacked some excitement, and I don't say that lightly. I spent a few weeks in Turkey a few years ago and of course I visited Istanbul, I've been inside the Hagia Sofia (or Ayasofya, as it's written in this book) and I've even been in the massive underground cistern (Basilica Cistern) that features prominently in the book. I can picture it perfectly, so you'd think that if anything, I'd love this book for choosing such great settings. 
 I think the main problem in the end is that although the Natasha Romanoff in this book did look and sound like Scarlett Johanssen's Black Widow in my head, she lost a lot of the wow factor and everything that makes me love the character, rather than just like her. The new characters, Alex Manor and Ava, just ended up being kind of bleh teenagers with an even more bleh romance. The focus of the story, on sisterhood and family, was appealing if a little overdone. 
 So basically the plot was great, the setting was great, the themes were great (with the exception of the obligatory teen romance), but the execution fell flat. Plus, there were enough editing mistakes that they became a distraction. I noticed this in the official Marvel Daredevil book too, so if that's related, the proofing and copyediting people really need to step up their game. 
 I think the biggest gripe I have is the "show, don't tell" problem of this book. There was a lot of telling and not so much showing. As much as I love the Black Widow character, I didn't feel for her here despite excellent reasons (view spoiler)[I mean, c'mon, long lost little brother?!? (hide spoiler)]. I almost wish that some of the talented fanfic writers I've found over the years had gotten a chance to try their hand with the same plot and characters - but then again, there's something about the lack of constraints in fanfiction that makes it easier for authors to write characters that readers can emotionally connect with, even when they are borrowing the characters from their original creators. 
 What I really wish is that Marjorie Liu could write a full length Black Widow novel. I've read her other works (Dirk & Steele #2, Shadow Touch, in particular) and she handles the beauty, menace, and mystery of Russia perfectly. I suppose she's too busy in her career to be doing these little projects though, which feels like Marvel trying to cash in on the popularity of YA publishing.