Two very different movies were made about this book: "Charly" starring Cliff Robertson and "Flowers for Algernon" starring Matthew Modine. The movies were made years apart and have very different vibes for the way that Charlie Gordon was portrayed reflecting different philosophies of acting at the times they were made. Cliff Robertson won an Oscar for his portrayal of Charlie Gordon.

Full text:

https://www.kkoworld.com/kitablar/deniel_kiz_elcernon_ucun_g...

Somewhat similar plot in this novel: https://en.wikipedia.org/wiki/Camp_Concentration