Recursion by Blake Crouch
What if you could go back in 'time' and fix something in your life – would you do it? To save your child? To become wealthy?
This book is about a scientist who invents such a machine to go back in 'time' and how this utterly fucks up our world. Why do I keep typing 'time' in quotes? This machine actually transplants the consciousness of the person into an earlier memory. Of course this sort of 'time' travel is not without its side effects.