"Flowers for Algernon," by Daniel Keyes

A modern American classic that has always remained in print since its 1966 publication, this shorter novel has also had its share of controversy with regular calls for banning. Get ready for a unique read that will have all your emotions going--prepare those around you for potential outbursts, lol. If you need anymore encouragement, 680,000+ readers have collectively rated this book a very high 4.2 out of 5 stars. Also, it has been adapted into a 2000 film starring Matthew Modine and Kelli Williams, if you want to follow up the book with a viewing.

From Goodreads:

Winner of both the Hugo and Nebula Awards, the powerful, classic story about a man who receives an operation that turns him into a genius...and introduces him to heartache.

Charlie Gordon is about to embark upon an unprecedented journey. Born with an unusually low IQ, he has been chosen as the perfect subject for an experimental surgery that researchers hope will increase his intelligence – a procedure that has already been highly successful when tested on a lab mouse named Algernon.

As the treatment takes effect, Charlie's intelligence expands until it surpasses that of the doctors who engineered his metamorphosis. The experiment appears to be a scientific breakthrough of paramount importance, until Algernon suddenly deteriorates. Will the same happen to Charlie?