I almost gave this 4 stars but there were a couple of small logic failures that weren't important to the plot but noticeable nonetheless.
I liked Maggie and her parents a lot; most of the time I liked her grandmother too, although Byron uses her too blatantly as a device to further Maggie's investigations. There's a nemesis in this story in the form of the Chief of Police; the result of an old, old family dispute a la Hatfields and McCoys, but Byron manages to make this antagonism believable; while his antagonism is unhidden and dishonourable, he never breaks the law or does anything beyond believability. This realism makes his nastiness more effective.
The atmosphere is fantastic; very recognisable as Louisiana's bayou country, complete with strangling humidity. There's a thread of romance running through the story that's good: well-balanced and realistic.
The murder plotting felt manipulated, as though the author thought "I'm going to twist this up so much NOBODY is going to get it!". I didn't get it, that's for sure, but I'm not sure I actually bought it either. It left me thinking "oh.", not "oh, wow!".
Plantation Shudders was an Agatha finalist for Best First Mystery, and I can see why; even though it might not be the strongest in plotting, the author infuses a depth into the story and the characters by seamlessly interweaving topics like autism and cancer that never feels overdone. There's a richness to the writing that is definitely appealing and I enjoyed this book enough to eagerly look forward to her second.