I really liked this book. Carrie was someone I could relate to well, even though I'm not a teen genius. :) But I was always the youngest in my class, as well as naïve--which made me feel even younger, and had a strong sense of what's right and wrong. I was far too shy to preach my beliefs and lacked the self-confidence to judge how others made their choices, but I remember feeling the way Carrie felt through much of this book.
The story is on the slower, quieter side, and it's all about Carrie's growth as a character. It wasn't difficult to figure out where the story was going or who she was going to end up with, but I thoroughly enjoyed the journey getting there. Carrie is funny in a zinging kind of way, and her observations waste no time in getting straight to the point. I loved this.
Even more so, I loved how she starts out as a judgmental, holier-than-thou loner, and gradually starts to the world through other people's eyes. This changes her perspective in ways she doesn't expect, and it's entertaining to see her genius brain try to work it out.
If you're looking for a good character-driven story where the main character goes from unlikable to likable, this is the story for you.
Side note: this book was presented to me as YA, but it's not really. It's an adult book with a teen main character, which also has crossover appeal. So, while I wouldn't classify it as YA, I can see many teen girls enjoying it immensely.