Reddit mentions of The Longest Day

Repercussions set forth by a misguided civilization unleash events difficult to predict or control which ripple through space and time affecting the lives of several characters simultaneously. As such, a young man living in the Dark Ages, occupied with mundane activities notices something strange about the world he lives in. Eventually, he acquires a mysterious device which seems to be at the heart of these phenomena. Soon he finds himself lost in unknown versions of reality and must find his way back to loved ones while filling in the missing pieces of his own personal story.

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Get it here: https://www.amazon.com/dp/B07P1K6LR4