This book isn't as bad as many people say it is. The best dialog is lifted from the book, and while nearly every character (except the sheriff) is a bit "cardboard cutoutish," I don't necessarily think that that's a bad thing.
The book is about an old time cop's attempt to understand what the hell is happening in his county when drugs really hit the area in the late 1970s and early 1980s. Each chapter starts with a reminiscence, and the chapter kind of sort of addresses the issues he raises in the reminiscence. Through the chapters, however, runs the story of a guy's discovery of some drug money, and his increasingly forlorn attempts to avoid the guy who is trying to reclaim it.
As I said, I don't think the book is as good as the film (the book doesn't have quite the pacing that the film does), but it's not that bad either. You just need to think of it as a guy reminiscing about the past, rather than a linear thriller. You'll enjoy it better if you take that approach I think.