Woah, that was something, wasn't it? 
I usually write reviews right after I close the book but I felt like I needed a bit more time to digest this one.
It had me from the first page (well, it had me from the blurb) and it did not disappoint. This is the story I've always wanted to be told, even as a kid, and I don't think 5/5 even covers it. I always wanted there to be a Library, and to be a Librarian like Irene. I've dreamt of writing this book. Except this book is even better than what I coulda done. 
It took a while for it to arrive to my local library (COVID and all) and that built up a lot of anticipation... then I didn't really dare open it in fear of disappointment, but disappointment was not what I got!
It starts fast-paced, and you learn more and more as the story goes but it never slows down. There's enough worldbuilding in this first book to fill quite a few novels, and yet it's only hints at a much larger universe, really. The main character, Irene, is really likeable, and so are her two sidekicks. I loved to hate Bradamant and I'm really hoping we see more of her. But what really got me was the worldbuilding. It's complex and layered and you can feel there's so much more the author's not telling us. It can feel a bit too much at times, but after all the centre of this novel is a chaos infestation, so it wouldn't be that good without a bit of overwhelm and, well, chaos. 
Now, if you don't like weird crawly insects, or spoilers, don't read behind the cut but

I really, REALLY hate silverfish. I know they're harmless, but I've never lived in a place without the occasional silverfish in the bathroom at 4am and they disgust me. make my skin crawl. And you know what, whenever I read a book, there's mice and cockroaches and stuff, but I've never read a book that even acknowledges the existence of silverfish. Before this one. And let me tell you, it worked VERY WELL at giving me that horrific shudder. I was right there with the characters and would've very much jumped on the table. 10/10 horror mastery.

Now I gotta get my hands on the next volume. And the next...