The young characters are not only learning about love and honesty, but also hidden agendas. They learn that not everything is as it seems, decisions are not always easy, in other words adulthood does not bring all the answers.
If you wish to analyse it further rather than just see it as a piece of fiction you can see a political tone to the novel.
The relationship between Peeta, Katniss and Gale is developed further, loyalties and romantic feelings between them being delved into throughout.
By the way there is a new genre creeping onto the bookshelves ‘New Adult’ which is YA with sex, odd really surely a new adult is just an adult.