You will either find this one fascinating, or toss it in frustration.

The concept of recursion will be familiar to math folks and programmers. The repetition of particular commands, until a goal is met, a non-programmer's incomplete definition, gives you the broad plot structure of this novel. Helena Smith is a scientist who believes her life's work is to create a device that will preserve the memories of those losing memory, like her mother, suffering from Alzheimer's disease. She sacrifices everything to develop the scientific knowledge and technology to create a memory chair, where memory can be stored and revisited. Meeting Marcus Slade, billionaire who wants to change the world, enamored with her project and seeing far greater potential, Helena believes she can make this a reality. We unwittingly enter the story at a midpoint--the chair not only preserves memory, but enables the subject, with use of a sensory deprivation pod, to "die" and project themselves back to a chosen period of life, essentially resetting their life clock, with all other memory intact--a re-do. When we meet Slade, the chair has existed for years, and he's experienced numerous re-dos, to the point that he has amassed a fortune and manipulated Helena into developing her technology to the point where this memory travel is possible for his purposes-- living innumerable lives, having countless experiences.

Enter Barry Sutton, NYC detective who observes up close a case of "false memory syndrome", thought by the CDC to be some sort of neurological condition, leading to an increasing run of suicides. There is no such syndrome, merely people who received dual sets of memories, related to individuals who have traveled in the chair, upon reaching the moment when both time frames meet, receive all former memory of the old time span, equally vivid as their current set of memories. Severe confusion about what is their "real" life--spouse, children?-- leads to suicide for many. Slade is making money with his covert operation, Hotel Memory, in NYC, tripping people back for re-dos, leaving a wake of collateral damage in their relations. As Barry tries to figure out what is going on, he and Helena finally meet, and not a moment too soon. Helena knows that humanity isn't prepared for the magnitude of what she has created under Slade's direction, and she can foresee the potential dreadful consequences.

The worst comes to pass when DARPA takes over the technology, and the device is inevitably disclosed on WikiLeaks. This rapidly leads to an arms race of mind-blowing proportions, with adversarial nations attempting to out think one another for advantage. Equally appalling are the terrorist scenarios taking place, a repeated torture for world populations. Crouch does an amazing job of depicting the scenarios that would surely play out should this capability fall into the wrong hands. Helena and Barry sacrifice many years attempting re-dos of their lives to prevent this, and pre-empt the chair's creation, failing many times over. I will not ruin the end for you, but I encourage you to take this wild ride and read Crouch's book. This is a difficult concept to describe, while staying logically consistent and driving a suspenseful plot to a satisfying conclusion. Crouch does as good a job as anyone, and it is fun to read how he does it.