So I had to check this book out from the library so that I could continue in the series and be ready to read the e-galley of the 4th one that I have. Now, I only gave the first book in the series a 3 out of 5 stars, but I liked this one even better than the first, and gave it a 4 out of 5. If you haven't read the first one, you might want to stop here, as there will be spoilers.So we're back with Gemma, who had to leave with the other sirens at the end of the last book, because they'd threatened to kill her sister, and her boyfriend Alex, if she didn't. So her sister, Harper, must go home and tell their dad that she ran away. But after all she'd seen, the terrifying bird creatures that the sirens could turn into, and the dead body of their island friend, Bernie. So now Alex and Harper are trying to do what they can to find Gemma, as well as figure out what was going on. They know there is something to do with mermaids, but what about the horrible bird creature? So they begin to do research, specifically at the library where Harper works. And that is when they find information about sirens. And they get a somewhat unlikely helper, Marcy, the unique girl that works with Harper at the library. Daniel is still trying to get through to Harper, it is so obvious to both of them that there is a spark, but Harper doesn't want to have to worry about Daniel. So, she tells him they need to stay apart. Meanwhile Gemma is trying to fight the curse, refusing to swim in the ocean or feed. But she gets sick, to the point where her hair is even falling out. While Thea seems to be more helpful now, Lizzie and of course Penn are still as evil as they seemed before. Finally Penn orders Gemma to swim. And soon Gemma begins to feel better. So her thought is to swim in the ocean and continue to try to eat regular food. Until a mishap occurs, where Gemma loses control. Around the same time, Harper and Alex, with some help from Daniel, figure out where Gemma probably is, and they go to try to bring her home.I won't go on, I'll leave the rest for you to read and find out. As my issues with the first book had to do with not knowing some things, we do now begin to learn some of the background of the sirens, and how they live. But we also get some new questions, questions that even Penn and Thea don't know the answers to, but feel the need to find out. I must say I'm glad I'm going to be able to go on to the next book as soon as I'm done with this review, because I need to know what is going on. Also, the cover of the third book? It is really good! And from that cover, I had some ideas of things that happened in this book, or an inkling of some things, so maybe seeing the 3rd cover was a bit of a spoiler or hint.