The perfect mix of plausible time travel accompanied by real-life conundrums. An entertaining exploration of how our choices matter and how the choices of others alter our own realities. 
 Similar to Ender's Game, I won't discount the idea that the futuristic science of harnessing the power of the Earth's rotation described in this book can one day bring about a boundless renewable source of energy. Because as William Arthur Ward says, "If you can imagine it, you can achieve it." 
 (view spoiler)[And whoa dudes, the twist when Tom uses Lionel's time machine then spends the next 50 years in backwards motion? I was so not expecting that. (hide spoiler)]