I’ve seen so much debate about this on forums! The book’s labeled YA, but that 'spice rating' folks talk about is very mild, really more just suggestive tension than anything explicit. The real sticking point is the violence and moral grayness. The main character’s a pirate who’s charmingly ruthless, and there are plenty of non-graphic but still intense scenes involving threats, kidnapping, and swordplay.
I’d say it’s fine for older teens who are already consuming similar fantasy-romance hybrids, but maybe not for a younger teen just dipping their toes into the genre. The narrative style is fast-paced and fun, but the emotional payoff hinges on enjoying a morally ambiguous heroine. My niece, who’s fifteen, loved it, but her mom (my sister) skimmed it first and was glad she did. The cover makes it look like a straightforward adventure, but the blurb hints at the darker edges.
Ending felt like a setup for the sequel, so the commitment is more than one book.