Thank you to Orbit Books and NetGalley for providing me with a copy of this book to read and give my honest review. The opinions expressed here are my own.
I was excited for this second installment of this story. If you haven't read the first, you absolutely must in order to read this story. While the author does a good job reminding you of background, you will not understand much of what happens without reading the first.
Also, know this is told in epistolary (letter) format. I had not read anything like it before the first book and enjoyed it so much more than I ever thought I would. I truly thought I'd be bored. But the author does a fabulous job of presenting all different points of view to really shape the story and the relationships between the characters.
These books definitely are ones that have you stretching your imagination to understand the world. It's pure fantasy with characters living both above and within the water. The author really does a great job of building this world out even more than you know from the first book. She expands where they travel and how and with whom. Plus she introduces a new group of characters.
I will say there were times I had to back track to know what was exactly happening (thus only having a 4 star review from me). You definitely have to focus all your attention on the story and not be distracted while reading this.
I liked the mystery and how it unfolded. Plus it's ensconced in academia, which is always so intriguing to me.
There is a ton of diversity in these books ranging from mental health representation to LBGTQ+. Lots of characters with differing personalities and relationships to follow and understand. 
And the romance! Its sweet and endearing. If you're looking for sexy and explicit, you won't get that here. You get bare bones attraction and a love that grows organically.
If you're looking for a whimsical duaology set in a underwater/surrounded by water world with a fantastic array of different characters with tons of representation, check these books out!