***Note: this review assumes that you've read the book.***
This book is not deep, but it's fun, and the entertainment value relies primarily on its humor, which is sometimes quite clever. The main character, Emma, has a snarkiness that's (mostly) endearing, and I'm impressed with the bold way Banks writes her voice. Banks goes full bore with sarcasm and comic scenarios, without worrying about the consequences.
That said, there were giant flaws with this book. Perhaps a literary analysis isn't fair, and the book is meant to be light and "consumable," but I have a compulsion to analyze, and that's why I'm here.
First-person, third-person. Emma's sections are told in first person, and Galen's are told in third-person, but from his POV. I'm not sure what this achieves. I think we would have felt closer to Galen if we'd heard his actual voice.
Character depth. The characters are mostly two-dimensional. Emma is witty, cynical, and snarky, but not much more. We're told that she likes history, but we only see a minor obsession with not-very-esoteric facts about the Titanic. We're told she mourns her friend Chloe, but she never seemed genuinely changed from the experience. (To her credit, Banks gives Emma a several-week mourning period, but when Emma's ready to re-join the world, Chloe barely figures into her emotions again, other than a few instances of lip service to the tragedy.) I was somewhat disturbed, rather than amused, by Emma's temper, which treads very close to slapstick but has real-world consequences. Galen is a pretty typical, post-Twilight hottie: perfect in appearance, domineering in his "protectiveness," fixated on aspects of Emma's looks when he admires her (her soft curves, her hair the color of the moon, her crimson lips), and keeping secrets rather than speaking to her honestly because she's "not ready for the truth." Just as we're told but not really shown that Emma loves history, we're told that Galen is extraordinarily loyal to the Syrena. Rayna is an upstart, but not much more. Rachel is almost comically one-dimensional--she's there to help Galen troubleshoot the human world, and to call everyone "sweet pea" and "honey" and make them seafood meals in her high heels (this is the genius who can hack computer databases?). Toraf is a strange combination: the most sensitive character in the book, who is inexplicably dense about Rayna's rejection of his advances (more on that later).
The plot. This is mostly about Emma figuring out what she is--half human, half Syrena--and setting up the geopolitics of the undersea world for the next book. Emma is from the house of Poseidon, Galen is from the house of Triton. Galen's brother Grom is supposed to marry the firstborn of the third generation of the house of Poseidon (which might be Emma) to preserve the "gifts" that the two founders left to their kind, etc. Nothing really happens that's not a standard linear set-up for the next book. That is, there's no engrossing story arc here, just a budding, thwarted romance between Emma and Galen--a love that is at first forbidden (so neither admits it aloud), and then the problems are surmounted, and then it ends with their love possibly being compromised again, because Paca's gift is disproved. (Nayla is alive, so presumably Grom is still mated to her, but not unless Toraf reaches Grom in time to tell him). There is no satisfying ending, other than knowing that Galen and Emma have finally professed their love for each other. (We of course suspect that their love will undergo a trial in the next book.) It ends with the revelation that Nayla is Emma's mother, practically in mid-sentence.
Blushing. This is just one of the YA tropes that is ladled heavily and without remorse in the writing.
This is not a Popyeye cartoon. There are so many scenes that are cartoonish, and I just didn't know how to take them; Emma pushing Rayna through a plate-glass window, across a beach, and into the water in one long cat fight, while Toraf and Galen watch, bemused; characters vomiting over the least thing (the idea that Emma will die of old age before him is enough to make Galen vomit in the sink until the drain can't take it); every scene with Rachel in it; Emma and Toraf making Rayna jealous with a kiss; Rayna splitting Toraf's lip when she wakes up and finds him sleeping next to her in her bed...
Rayna and Toraf. This has caused a problem with other readers, and for good reason, I think. There is a distinct mixed-message about feminism in this book. Emma pays lip service to going to college and not giving her life over to a man (in a monologue dripping with "See, reader, this book isn't falling into the Twilight trap! Emma isn't Bella Swan!"), but then Emma spends the whole book mooning over Galen, sleeping through class, and at one point joking (maybe sarcastically) that the only reason she isn't one of "those [Bella Swan] girls" is that Galen won't have her. Galen treats her like a child; she is feisty but doesn't really confront him. It's hard to understand what the author is trying to say, when in third-person we hear that Paca has a plain face, but "not the kind of plain that you feel sorry for." But the worst slip-up with feminism is the way Rayna and Toraf get together. Even if you accept that the Syrena have arranged marriages, and that in their culture Toraf is somehow allowed to marry ("mate with") Rayna against her wishes and without her being present, you can't escape the scene in which Rayna changes her mind about Toraf. After rejecting him with some fairly solid "no" language (and physically abusing him to send him the message), and after reading that Toraf basically stalks her despite her telling him to go away, it was inappropriate that Rayna is made to "realize" her love for him when he kisses Emma on the beach. After that, Rayna the wild-cat becomes a tamed kitten, in the way Scarlett O'Hara was giddy the morning after Rhett Butler forced himself on her.
This book is meant to be lighthearted, and with all the joking and slapstick in the book, I don't think Banks wants us to take it too seriously, but it feels like sloppy writing to allow old-fashioned, anti-feminist, beauty-culture messages slip through when the point of the book isn't to make a commentary on them.