This review was written by AD_Productions. He has a wonderful and unique fan fiction that is begging to be read. If you have time on your hands and like good stories, go and read it! 

Cover: 17/20 

The only nitpick I have is about the title spacing. If I were you, I'd just write Daughter of Neptune on top, leaving room for admiring the cover, which by the way is quite fitting; it reminds me of the deep sea, which ties is nicely with the whole "I thrive in chaos" mantra that Siren keeps repeating. The title is a bit generic, but considering that pretty much 95% of the things that happen to Siren happen because of the fact she's a daughter of Neptune, it's certainly fitting.

Description+Tags: 16/20 

*****
 A half-breed is faced with hate and depression when she is claimed by New Rome. After spending two years there she is offered a chance to visit the famed Camp Half-blood, home to her legendary brother Percy Jackson, but she faces uncertainty and fears the unknown....what can she do? 

(Includes symptoms of depression and PTSD)

 I do not own any PJO or HOO characters 

*****

 Nothing too fancy in the description. There's a character that was and is hated by the people around her, so what happens if she changes environment completely? Between the cover, the description and Siren's characterization, I'm starting to see a pattern; It's like Siren is directly saying to the reader "this is who I am and this what happens to me. Deal with it". 

Maybe I'm just imagining things, but if that's on purpose, chapeau. about the tags...aside from the "standard" ones like 'percyjackson', 'camphalf-blood' and similar, you basically threw in a bunch of generic adjectives. Now, 'cool' and 'awesome' are perfectly fitting for your story, don't get me wrong, but they don't tell me anything about what to expect by the story. Those adjectives are fitting BECAUSE they're so generic. Then there are the usual disclaimers, which I personally think shouldn't be required, but you did the right thing by writing them. Nothing to say here.

Beginning: 15/20

 A+ for effort, B for execution. You establish right away Siren's behaviour towards others, her peculiar situation, and how people treat her. I wasn't surprised at all when she did...what she did in the climax of the book, because I knew from the beginning that Siren was capable of that. I say B for execution because you set up this "Serious crime" that Siren supposedly committed, but the reader doesn't get to know a sliver of it. 

The only thing we know is that literally everyone hates her; even Reyna, who is usually pretty level-headed, treats her as the lowest kind of scum. She wasn't nearly as hostile towards Octavian, and the guy brought CJ into a war that would've resulted in Gaia rising. You can't be worse that that. So either Reyna is severely OOC, or Siren actually did something evil, and the reader cheers for the actual villain of the story. It's not the first time that happens, you just set things up without a payoff. 

Now, I understand this book is meant as part of a series, so it's totally ok not to answer every single question, but at least give the reader SOMETHING, or it feels like this book is just a huge setup for the actual story.

Conventions: 14/20 

 In the beginning it needs some serious reworking. Missing punctuation, weird sentences... but then it gets much better aside from the occasional typo that everyone can easily ignore.

Characters: 18/20 

 This is definitely the best thing about the book. Every character has its place in the story, and Siren's arc is very believable. Fortunately, I don't have any experience with PTSD, but a friend of mine has it, and I know from her that while friends and family (or lack of) aren't an immediate "Everything's OK" button, they certainly have a huge impact, and it shows. We start with a Siren that doesn't even question people that call her a monster, we end with a Siren that stands up for herself and isn't ashamed of being daughter of Neptune. Every other character has a character arc as believable as hers, except for Reyna and Pandora, which is why you didn't get full score

Overall score: 80/100 

This is a great fan fiction that can become awesome with just a little tinkering. My main concern is, again, setups that never receive their payoffs. I'm not saying you should give every answer right away, but at least give something to the reader they can speculate on. This can include Siren's "crime", how her mother and Poseidon met, why Reyna and almost the entirety of CJ is so hostile, why is Octavian allowed to exist after what he did...

Also, another tip. Don't rush important scenes, give them the right time to play out. An example is the climax. You did an excellent job at setting it up, but when finally Siren snaps and reacts...everything happens in two short sentences. Try to apply both this tips, and your fanfic will become a masterpiece.

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360_Productions here! The reason I didn't write the review myself is because of my bias. You need other opinions, especially since you've heard mine before!