It's about 2 buddies, their girlfriends (one of whom has a much bigger part than the other) and one of their mothers as they (for their different reasons) degenerate into severe, prolonged, hard drug use.
The younger element of the book start off trying to sell a little heroin to get out of their lower middle class/working class environment, while the mother gets hooked on diet pills when she's given the potential chance to get on a game show.
Initially everything seems to go "swimmingly" in the book, but as it progresses, we watch their slow degeneration into the out-and-out junkies they become. It is this part of the book that you will find harrowing, as they becoming increasingly willing to prostitute their morals to feed their drug habit.
Im short, it's a depressing, but interesting, book that will make anyone who reads it think twice about drug use.