I thought this had great potential, but although it was fast and a solid teen parallel world story, it lacked a little in depth and consequence. Singletons could have been explored more, and there was very little in the way of science for the reader to enjoy, especially given that a lot of learning has to happen in order for John to progress with the plot of the story. Still, this was neatly done and I have no problem recommending it to someone new to the genre or in it for a quick romp.