Flowers for Algernon by Daniel Keyes - 3 out of 5
I'm trying to work my way through the SF Masterworks series and this is number 25.
The book is written in the form of Progress Reports (basically diary entries) & follows the progress of a mentally retarded man (Charlie) with a low IQ who undergoes an experimental operation to boost his intelligence.
Aside from the “experimental operation” angle, there is very little SF in this novel, it could easily pass for a main stream book.