I really enjoyed this cross of a coming of age story with an end of the world theme. Not to give too much away, the earth's rotation starts slowing, make each day longer. I (as an adult) was less interested in the main character's middle school drama, I give kudos to the author for the fresh take on a world-wide disaster, especially since there was not a zombie in sight.
My husband and son(two physics majors) had major problems with the hard science, but since this is fiction, I can suspend my disbelief. What I really liked was the societal ramifications of figuring out how to calculate a daily clock, and how people who calculate it differently relate to each other.