I haven't read the first book in this series, so I'm not sure if I missed any deeper meanings, but I didn't feel confused like you sometimes do jumping into book 2.
You can't go wrong with a fairy tale, and this Caribbean fairy tale is exciting.
Corine is part jumbie (which my spell check is also distrustful of), and so the townspeople don't trust her. There is an earthquake and when some kids go missing some townspeople blame her. She meets with Mama D'Leau (a scary sea witch), who tells her what she should do, and so Corinne embarks on a long trip with some mermaid friends. On their way, they come across a wrecked slave trading ship and realize that the mermaids used to be girls from Ghana. This story is well written, and the pace is just fast enough. I liked that it kept me guessing and that there were larger themes woven into the plot like slavery, chosen family vs. the family you are born with and what happens when fear and hatred take root in people.
I could see pairing this with some nonfiction on the slave trades and make a mini unit study out of it. I'd suggest Shackles from the Deep By Michael Cottman. For some reason my review didn't carry over from my old blog but here it is on Goodreads.
Rise of the Jumbies By Tracey Baptiste