Summary: In a post-apocalyptic world air pollution made society send selected people to a human-built underwater city to preserve humanity. After a few generations sirens developed, whose voices could influence people's minds. Sirens are respected but mostly feared and get taken by the government so most hide their ability.
If there are multiple siblings, one can choose to stay Below or risk going Above. The main character Rio has always wanted to go Above but her sister does instead. The book is focused on Rio trying to reach her sister.
I enjoyed this book. It's an easy read that didn't get boring. It had a romantic subplot that didn't feel forced (for once). Some characters could stand some more development or backstory but even then the world building is decent. The author makes it a point to describe the bubble world they live in thoroughly so we understand significant details later. There are family secrets, government secrets, secrets in the Above...it's all very secretive, but in a good way that doesn't feel exasperating.
Underwater dystopian secretive fantasy. Very good.