I would not recommend this book to teens, or even fans of YA fiction. It is written in such a way (that I'll get to soon enough) that it would have more appeal to fans of adult sci-fi, British mysteries, or especially adult British sci-fi.
There is something very off about this book. Pop culture references that don’t belong in the future, already uncommon English idioms spoken by aliens, uncharacteristic dialogue, strange devices that make the future setting awkward and unbelievable (Shock Socks? Email sticks?) all make Neptune’s Tears an awkward attempt at a dystopian romance set in the near future on an Earth that has seen the arrival of extremely human-like aliens.
The tone of the entire novel is distant, sparse, and disconnected. Teens will not be able to relate to the characters. The dialogue is not realistic. The characters' actions are barely convincing. The protagonist's thoughts and inner dialogue is fine at times, but it would have benefited from being told in first person to jump that gap between the reader and the story.
The plot was believable at first, but quickly spiraled into something strange and convoluted. I didn't believe for a second that the love interest was actually an alien. I didn't understand why the best-written parts of the story were the protagonist's visits with the dying old lady. I didn't feel like her interactions with her friends were things that teens would actually do. The romance was very bland.
And finally, the twist at the end came far too late. There were no hints leading up to it. It came out of nowhere and made no sense and will infuriate readers. No spoilers, but seriously-it's not good.