The Night Circus is not a young adult book. It is purely adult fiction, with characters over 18-years-old and mature scenes. It also has a lot more descriptive writing and symbolism, which is less common in the young adult genre.
Yes, the Night Circus does have romance and a swoon-worthy one at that. In fact, this book actually features two romances between two couples. However, the romance between Marco and Celia is the primary romance.The second romance is not introduced until halfway through the book.
Yes, the Night Circus is an enemies-to-lovers story, given how Marco and Celia are rivals and supposed to be enemies. However, this romance isn’t necessarily the enemies-to-lovers trope you might expect. Enemies-to-lovers brings to mind characters who go from hating to then loving each other. Our main characters are only supposed to hate their opponents.