"Flowers for Algernon" is an all-time classic that I love.
Charlie, a mentally disabled man, was given a chance to have his
intelligence experimentally enhanced as Algernon, a lab mouse which
had gone through the same procedure. The super-IQ Charlie
experienced major changes in the way he lives his life. All went
reasonably well until Algernon started to deteriorate unexpectedly.
Charlie knew then that the same thing would happen to him and
invest all his energy in the quest to preserve his IQ. One of the
last scene of Charlie praying for his language ability touches me
deeply. I then realize how lucky we are even to have the simple
blessing of being able to read and write.