Recursion

Helena Smith, a brilliant neuroscientist, invents a device called the 'chair' that allows people to record and relive their past memories, effectively allowing them to travel back in time. This technology was originally designed as a treatment for Alzheimer's disease to help her dying mother. However, it is stolen and weaponized by a powerful tech billionaire.

The co-protagonist is Barry Sutton, an NYPD detective who investigates a mysterious affliction known as 'False Memory Syndrome' that drives its victims to remember lives they never actually lived. His investigation brings him into contact with Helena Smith and her revolutionary technology. Together, they race against time to stop the complete collapse of human reality.

The time loops are triggered every time someone uses the memory chair to regress back to a specific point in their past, thereby creating a completely new timeline that overwrites the old one. As the technology becomes commercialized by the Cornerstone agency, the continuous overwriting causes widespread temporal instability. This eventually leads to 'The Crisis,' a point where reality itself begins to degrade.

The protagonists ultimately realize they must reset the timeline all the way back to before the memory chair was ever activated to save the world from destroying itself. They succeed in restoring the original, unaltered timeline at great personal cost. The story concludes with Barry retaining a lingering memory of their alternate lives together.