The Dark Tower #1 by Stephen King

A lone, relentless gunslinger named Roland treks across a dying, desert world in pursuit of a mysterious figure called the Man in Black, driven by a consuming obsession to reach a fabled central tower that holds the fabric of reality; along the way he confronts a haunted frontier town, rescues a troubled boy from another world, forms an uneasy bond with him, and grapples with the moral costs of his quest as remnants of a collapsed, technology-haunted past intrude on his relentless pursuit.

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