First of all, it took what felt like FOREVER to get through this. I kept glancing at my progress and seeing I hadn't really made any. I'm pretty sure I was bothering my fiance to no end with my constant "this book is SO boring!" and "I'm never going to finish!" I know you're probably thinking "then why did you finish?" but I'm always really hopeful when it comes to these types of things. I simply want to book to better and hope by finishing it it'll be so. In this case, it definitely wasn't so.
When I first started I felt like I'd been dropped into an alien world without being given any sort of direction. Some things cleared up a bit as I got further into the story, but I was left in the dark about many things. I never did get a picture of what trannies or elports looked like so I ended up having to imagine up something all on my own. I was very disappointed in the world-building here. Karr built a whole new future world but didn't bother to explain much to the reader.
Another disappointment was Nina herself. She was so annoying! She sits there and accuses Sal of using her and then continues to be friends with someone who's acting no different than the way Sal had been acting. She goes on and on about not wanting to be "sex-teen" to the point that she treats Sal badly. Speaking of Sal. He wasn't a fantastic love interest or anything, but he really wasn't that bad either. He was nice and a teensy bit mysterious, but that's about all I know about him.
The writing just made the story feel a bit forced, as well. The dialogue was often odd and awkward and it felt like things popped up out of nowhere just to keep the story going. There was basically no flow at all.
For all that ranting, there were a few things I liked about XVI. Karr tackles the issue of teen sex in a new and unique way. It felt like she wasn't afraid to get in there and get her hands dirty. And while nothing was particularly explicit, it felt like she wasn't watering down the issue for the teen audience either. And another little random thing I enjoyed about the story was the fact that everyone ate vegetarian in this future world. I like this because 1) I'm a vegetarian and 2) it's actually a real issue people don't normally think about.
Final thoughts: I wouldn't actually recommend this to anyone, but I also wouldn't tell them specifically not to read it. There are some interesting ideas and issues worth taking a look at in this book.