Flowers for Algernon (Daniel Keyes, 1966)

Charlie Gordon, IQ 68, is a floor sweeper, and the gentle butt of everyone's jokes, until an experiment in the enhancement of human intelligence turns him into a genius. But then Algernon, the mouse whose triumphal experimental tranformation preceded his, fades and dies, and Charlie has to face the possibility that his salvation was only temporary.

Rating: 10/10

A similar book:
More than Human, by T. Sturgeon