Okay so I just read the reviews on Amazon for the three books you mentioned. I really liked the sound of Choke, it just sounded completely different from anything that I have read recently and I know that author also did Fight Club, which I've always wanted to read, love the movie, and I think Ame read it and liked it. So my vote is for that one.
But I will say that Sunshine also sounded interesting and I would read that one as well. Plus it sounded like an easier read and a little more light hearted. And if you are really worried about having time for a book, in between school work, then I would pick that one.
Also, when reading about Sunshine, I also took notice of two of her other books Beauty and Rose Daughter, and both of those sounded really good. I might have to pick one of those for the next time it is my turn, or just read them on my own if I can't wait that long. They are supposed to be re-telling's of Beauty and the Beast, and they sounded really interesting.