I really enjoyed this book as I've been going through an interest in the whole alternate universe theory lately. Roberson did a great job showing how a young girl who was very interested in Physics because her father encouraged it (he was a professor). The girl received an object she called the Sofia. The Sofia would allow her to explore different time lines - including being able to travel forward and backwards within her own time line. It's a lonely life, but she's very happy with her lot in life. I won't divulge the ending, but I was satisfied with this story. It's a very light read and Roberson does a good job explaining some difficult physic concepts.