I really enjoyed Legend, but it's not my favorite YA dystopian.
For one thing, the love story is ridiculous. Instalove all over the damn place, stretching my incredulity even further with the fact that the female MC is grieving a family member who died less than a month ago. Not really a sexy situation. The mystery's not overly interesting or new compared to other members of the genre. It's fine, but the government's plan has a lot of flaws that are glossed right over. I was also really put off by the formatting of the chapters. There's no reason for Day's to be in bold and it's never explained why June's are written like a police report when they're full of private feelings and things that would get her arrested. If your characters are well written, you don't need to resort to tricks to separate the POVs.
Still, I liked June and Day, and their struggles kept me going. The plot was fine, the writing was fine. There's nothing wrong, but hopefully the sequels get more right.