Beware! This book's title is pure clickbait. It's not really about any rules of time travel. It throws in a line about "rules" maybe twice, but they felt like afterthoughts to me. In my opinion, it's just lazy writing to justify a cool title—a title that gives the impression that there is something fun or interesting about this story. Let me assure you, there is not. 

This book is actually filled with one-dimensional characters who couldn't be likable even if they were portrayed by your favorite actor. The plot actually revolves mostly around traveling in memories. The bad guy is the typical mustache-twirling, gas lighting CEO. Around only to frustrate the MC from afar and to monolog for a little bit at the end. When the story finally progresses into the realm of "time travel," its only reasoning and explanation is that the silly human brain can't comprehend it, so we can't really try to explain it. In other words, it doesn't even try to bring the story together in any comprehensible way, which is the worst way to go about writing about time travel. I expected more reason and thought out of a book marketed as being written by a scientist. Maybe speculations on time travel would be better left to the philosophers instead. This was just dry, annoying, and silly.