When I got around to reading it, it started slowly. The point-of-view jumps around. It puts me in mind of Holes (if you've ever read that) with the shifts in point-of-view and setting (including time). It's a little hard to follow at first.
Luckily the language of the swamp, dripping with voice and beauty and nature's humor, kept me reading. Then I was hooked into the broken narrative that began spiraling together to form the meat and fun of this book.
The raccoon scouts of Sugar Man Swamp have been watching for decades, even if they never were quite sure what they were looking for and, if they found it, who to report to, unless it was the great Sugar Man himself, a giant of a Big Foot-type character. But where to find him amongst all the rattlesnakes? And 12-year-old Chap tries desperately to save his home and his family's business after his beloved grandfather dies. Then there's the bad guy, the selfish and mean capitalist without a heart, the guy you love to hate. Somehow Kathi Appelt ties all of these characters (plus some) together to form a cohesive and delightful story.
Did this book have an agenda? Yes and no. It was the kind of agenda I'm okay with. It wasn't overpowering. I mean, the characters were trying to save the swamp from wild boars and from being totally concreted over. It worked because the story wasn't only about that.
And the writing was good and intelligent.
My 10-year-old liked the book, and I don't recall anything objectionable (I admit I read it at least a month ago.).
My recommendation is to read it. You may need to start reading it out loud at first to help if you think your reader might struggle tying the broken plot together. It will take a few chapters, but then you both should be hooked.