For a good review and analysis read Cole Riann’s review.
This plot driven book is very busy, setting the worldbuilding and a set background for the rest of this serial. I call it a serial and not a series because that’s what it is –the beginning of a serial or an episode of a story that has an unfinished or a “to-be-continued” feeling to it --or at least, that's how it felt to me.
As a matter of taste, I prefer character driven stories than plot driven ones. If I love my characters I can forgive a lot, especially because I am looking first at the love story, and the rest is secondary. I did not get that in this story. The MC's meet, they feel an immediate attraction that seems irresistible, but it’s left mainly unexplained because of the fantasy aspect of the story. They also spend a great part of the book separated, so it was difficult to feel the intimacy that characters usually have in a relationship.
There is sex in this story, but I felt disconnected from it. Maybe the best way to explain it is that this book left me emotionally cold, but at the same time, it left me intellectually curious. AND I really liked Taren, our young, sweet merman.