Algernon is a lab mouse. He gets an operation that makes him really good at solving mazes, but then he gets dumb and angry and then he dies. But the story is really about Charlie, a retarded guy who gets the same operation a few months after Algernon does, and the same thing happens to him. It's kinda depressing because Charlie sees the deterioration of Algernon when he's smart and able to realize what's going on, and then he just has to look forward to getting dumb, angry, and dead.
Actually, the only part of the book that struck me was when the doctor mentioned the cause of Charlie's retardation. It's not trisomy or some other genetic abnormality that you just have to suck it up and deal with. It's phenylketonuria (PKU). We learned about this in one of my many genetics classes. It's caused by a mutation in the gene that encodes some enzyme responsible for converting phenylalanine into tyrosine. The problem isn't a lack of tyrosine (we get enough of that in our food), but in an accumulation of phenylalanine. I think the initial symptoms of PKU include funny pee, because there's a ton of phenylalanine in it.
The point is that Charlie's retardation could have been prevented, by simply putting him on a special diet. PKU is totally treatable, and it's not even an issue as long as it's diagnosed before too much brain damage occurs.
Of course, in the book they claim to have made him smarter by "speeding up all the processes of the brain" (and that's why he got dumb again-- his brain got old and senile), which is totally ridiculous, because it's not like his brain was underdeveloped; it was damaged by phenylalanine accumulation. Charlie wasn't going to get smarter with time, so speeding it up would not have had any effect.
Am I overanalyzing the science in this half-century old book? Probably. I'll be done now.