Emily discovers a ring hidden centuries before by Neptune. In anger, Neptune lays a curse on Emily, which she must remove or be doomed to live as human or mermaid, not both. The story line of this adventure is tighter than the earlier books, but Emily is still irritatingly weak and passive, taking action only when prodded by her stronger friends. In the third Emily Windsnap adventure, lightly illustrated like its predecessors, the half-mermaid heroine finds that her idyllic existence is beginning to tarnish. First, it seems her recently reunited parents may separate; then, Emily’s discovery of Neptune’s discarded wedding ring leaves her struggling under a curse that could erase one of her identities. Kessler expands the mer-people’s backstory here, providing greater perspective on Neptune’s wrathful nature. As with the preceding books, though, what will most delight readers are the details of undersea life, from course work in hair brushing to scale polish for decorating tails. Gr 3-6-Half-human/half-mermaid Emily should be happy. She's living with her recently reunited parents (a human mother and merman father), she has a best friend, and she loves her new school. Still, this third book in the series finds her preoccupied with her parents' escalating bickering. After awakening King Neptune's fearsome monster in book two, Emily has vowed to stay out of trouble, but that is exactly what she finds in a magic ring from the ocean floor. When the king finds out that she has hidden it from him, he is furious and puts a curse on her: at the next full moon, she will become all human or all mermaid, whichever he chooses. So begins an adventure that takes the girl to a secret castle where she learns that she may not be as unique as she previously thought. Kessler combines the whimsy of life as a mermaid with the problems of an average middle-schooler. She keeps the story moving, with each chapter posing a new problem. Plenty of dialogue and Ledwidge's soft, dreamlike line drawings add textual and visual interest, making for a zippy story in an attractive package. Fans of mermaids and things that sparkle are the likely audience for this light fantasy.-Adrienne Furness, Webster Public Library, NY Copyright 2007 Reed Business Information.