My mom tried to get me to read this book several times, first with her old copy, and then she bought me a brand new one. She kind of spoiled the whole thing for me when I asked her what it was about, which is why I didn't read it sooner. She was right though; it is quite an excellent story.
Charlie is an adult with a very low IQ, yet he has a huge ambition to learn. Because of this, he is selected for an operation that will make him something like three times smarter than he already is. He quickly surpasses even the doctors who performed the operation on him. As he finds out, life on one end of "exceptional" isn't so different from life on the other end of it. My emotional mom calls this book a "tearjerker," but it is definitely thought provoking.