I'm quite surprised that many readers regard it as a book about drug addiction and junkies of different types. I (as the title clearly states) mainly see it as an attempt of pursuing the American Dream, the one that grants all American citizens total and pure freedom. And so, since nobody really knows if the Dream is dead or not, anybody is free to try it out.
What makes it better than the film (if this was ever debatable), is the story-line and the stories behind the characters. Due to my bad memory, I can hardly remember the story in the film, I got stuck on some recurring images and that's pretty much it.
The book was written 30 years ago, but you wouldn't notice that. Well, probably if it had been recently written, it would have involved some computers or iPods :). I only regret I didn't read the English version, I'm sure I would have enjoyed the way Selby's messing with grammar and punctuation.