This being number six in the "Doc Ford" series by Randy Wayne White. It's an unusual outing for Doc. He discovers a dead body on page seven. Then there's about 200 pages of flashback, explaining how he got to that point. Then about 80 pages from there setting up the climax. And then the wrap-up is about 20 more pages; almost all of the action happens in those last 20 pages.
I am not one to second-guess authors, let alone truly gifted ones like White. But that's pretty far off the normal course of the typical mystery/thriller genre. According to the official website, the "ending of The Mangrove Coast has been called one of the most shocking in mystery fiction." I don't know about that, but it's certainly different; you might find it depressing. (If you pay attention to clues dropped here and there, you won't be too surprised by the big revelation at the end.)
Along the way, even though there's little action, things are pretty entertaining. White does a great job of letting Ford's first-person narration tell you more about him than Ford knows himself. Some sections reminded me greatly of the one-man bull sessions from John D. MacDonald's Travis McGee books.