A fairly enjoyable epilogue to the series. Answers the most important questions about the group from book 5 with a reasonable-stakes mystery.
Writer's perspective critique: The main character of this 1st person narrative gives a play-by-play on the colors of her eyes changing while she's not looking into a reflective surface. There's no plausible way for her to know this, and the eye color was not my most pressing question as a reader looking for follow up to the last book.
I have pretty mixed feelings about this series in general. The plots are wild enough to be superhero plotlines, the team's powers make them almost werewolves (there just aren't enough werewolf books in the world, y'all), and I like mysteries, but they work for me in sections. There'll be sections that I like and sections where I need to take a break and come back, maybe because it's really close to being what I want and is frustratingly not quite there, or because something just feels off.
As I read this in 2021, I think something else that could have been done differently is the approach to Charleston high society. I think the main character makes pretty clear how uncomfortable people with that much money are to be around and how outdated she finds the rituals, but I don't remember if racism, slavery, and white supremacy are ever brought up in that context. I think the patriarchy is. I don't know how, exactly, it could have been done, but it feels off that nothing related to the history of oppression gets mentioned in this story--which is set at a high society wedding where the bride has grown up ridiculously wealthy and is insisting on lavish traditions. I think it would have been good to see any of the characters expressing that awareness. For me, I can't think of rich people in Charleston, SC without thinking of the South and white supremacy.
The superhero plotlines are just a smidge grounded to make suspension of disbelief hold at times--in a Spiderman or similar universe, sure, but in an otherwise realistic world, the odds of some of this stuff working just seem really long. The mysteries sometimes work really well and sometimes get bogged down in science exposition from the characters that comes across like lessons.
(Spoilers)
For instance, at the end of this mystery, there's a notepad where the bad guy has taken the top page, and it's pretty obvious they need to pull the "shade out what's written on the page underneath" trick, which the protagonist gets to explain to her love interest because he's old enough for college and does this mystery stuff but has, I guess, never heard of it?
Maybe I want the authors to trust their readership more. It's a series about smart kids/nerds, after all, from the point of view of a highly intelligent teen, and it's likely going to appeal to smart young people. Trust the smart young adults (and those of us who remember being smart YAs) to grasp concepts a bit more quickly, or let the characters explain things to each other using pop culture references and allusions that would make sense for their personalities. Yes, the science facts are cool, but this is a fictional narrative and not a science lesson. This is also frustrating from a plot point of view. For intelligent teens, especially in book 5, they did some stuff I would have expected them to think through better--they rushed into a lot of traps and failed at a lot of strategic planning. It was very frustrating.
The characters' personalities are another thing I think need a bit more development. I've read all five books and this novella, and these main characters don't feel concrete for me in a way that characters in other books do. Hi and Shelton still feel kind of interchangeable in a way, say, Patricia Briggs' characters--even secondary characters, like Asil and Leah--don't really. Chance and Tory have the most interesting and developed personalities.
I'm really disappointed that the series ended without Chance and Ella joining the group. I know they have a rocky history with the main crew, and I'm not sure what the ethics of that should be, but I think it'd be good for Tory to have someone around who challenges her the way Chance does, and I'm really disappointed that she never really got to have a great female friendship. The authors have left it open enough that I could see this happening in a later story, and I'd like to read a next book if it comes out--especially now that the team has their powers under better control and we've made it through the origin stage--to see if any of that happens.
Lastly, I'm not really a fan of the Tory/Ben ship and how it goes down across the series and in this book. I don't want to be to hard on Ben for accidently being manipulated by a serial killer because he wanted to impress a girl (he is a teen), but the fact it took him so long to come clean about it once he realized things had gone bad seems like a big problem to me. And in this story, he's let his girlfriend think he's going away to college so he can surprise her with the news that he's staying in town to go to a military academy. Her parents and friends already know, so she's the last one to find out, and that leaves a bad taste in my mouth. It would have made way more sense and been better behavior for them to have decided what to do in honest conversations about what they wanted and what they were afraid of as a couple, and--given the whole "the four of us have a specific unstudied condition that could probably deteriorate at any time"--as a group of all four.