Recursion by Blake Crouch

What if someone built a machine that let you go back in time and correct all the bad things that happen to good people. That would be a good thing, right? It could also set into motion a spiral of other problems because you are altering the universe and you can't do that without implications like False Memory Syndrome. So while you don't have to lose a child or leave a murderer loose you will have blood running out of your nose and feel like you remember every detail of a life you have never lived. Helena is a brilliant scientist who needs to find a cure for her mother's Alzheimer's by studying how the brain processes memory. Her motives might be pure but not everyone sees this in the same way. This is time travel on steroids, science made simple and frightening complex at the same time as only Blake Crouch can do. It will scare you and make you question your own memories but you will greedily read this in one sitting.