'Recursion' (1959) by Blake Crouch

'Recursion' is a fast-paced science fiction thriller that explores memory, time, and the fragility of reality. The novel follows two protagonists: Barry Sutton, a New York City detective, and Helena Smith, a neuroscientist. Their paths cross as they confront a phenomenon called False Memory Syndrome (FMS), where people experience vivid memories of lives they’ve never lived. These false memories often lead to profound psychological trauma.

Helena's groundbreaking research into preserving memories for Alzheimer's patients takes a dark turn when billionaire Marcus Slade funds her work for more sinister purposes. Her technology evolves into a memory chair capable of transporting individuals into their pasts, allowing them to alter reality. However, every change fractures timelines, creating cascading consequences and rewriting history in unpredictable ways.

Barry becomes entangled in the chaos when he investigates a case involving FMS and discovers its connection to Helena's work. Together, they must navigate an increasingly unstable world where timelines collapse and memories of alternate realities haunt them. The story delves into their struggles to undo the damage and prevent the misuse of Helena’s invention, even as they grapple with love, loss, and the moral implications of rewriting reality.

The novel combines gripping action with philosophical questions about identity, the nature of time, and the choices that define us. Its intricate plot twists and emotional depth keep readers enthralled to the very end.