"Deep in the ocean, in a world not so different from our own, live the merpeople. Their communities are spread throughout the oceans, seas, and freshwaters all over the globe.
When Serafina, a mermaid of the Mediterranean Sea, awakens on the morning of her betrothal, her biggest worry should be winning the love of handsome Prince Mahdi. And yet Sera finds herself haunted by strange dreams that foretell the return of an ancient evil. Her dark premonitions are confirmed when an assassin's arrow poisons Sera's mother. Now, Serafina must embark on a quest to find the assassin's master and prevent a war between the Mer nations. Led only by her shadowy dreams, Sera searches for five other mermaid heroines who are scattered across the six seas. Together, they will form an unbreakable bond of sisterhood and uncover a conspiracy that threatens their world's very existence."
Deep Blue is a middle-grade mermaid novel. I found myself disappointed in the lack of character development and the obnoxious shallowness of the characters BUT it's a middle-grade novel. I don't read many of those, so maybe that was a case of me expecting too much? Probably.
On the bonus points side, Jennifer Donnelly has created a very richly imagined world. The physics don't necessarily work, but the concept of cultures, terms, dress and diversity in this world shows a lot of forethought. This is a big plus, as both a bridge between a fictional world and our modern one, and because it distracted me from the worst of my boredom while reading it.
I think you'll like this if you enjoy mermaid stories, middle grade novels, very quick reads, teenagers, and very pretty imagined worlds.