In Other Lands by Sarah Rees Brennan - YA book, but not shy about the sex. First half is a M/F romance, then it switches to M/M romance.
If you haven't read this, read it. Even if you don't read young adult fic. It transcends what most people think of as YA.
The main character, Elliot, in Sarah Rees Brennan's book 'In Other Lands.'
He's a bright, bitter, angry teenager who ends up in a military training camp in a magical land. Elliot is not popular or athletic, so in self-defense he wittily insults almost everyone he meets.
This doesn't always work out well for him, but it sure kept me laughing.