"The Samantha Project" by Stephanie Karpinski
This is a really fun light sci-fi book that is totally believable. With all the science out there concerning studying DNA and how to manipulate cells, etc. (can you tell I'm a scientist, with all my scientific eloquence?), it was totally realistic.
I loved the characters and the entire story line. It's very well written and so evenly paced, with one event flowing so evenly and nicely to the next. I will totally read the rest of the series. Way fun!