Mmm, I don't actually think it's really so bad it's good. It kind of goes past that hill entirely. Rather, my opinion on it is that it's one of the very, very few books that is so bad that it passes being good into being heinous, and goes so far into that area that it hits a wall of sheer hilarity. I can't think of a single other work of literature that reaches the second so-bad-it's-good marker.
Read. Now. Alcohol is advised.