How the One-Armed Sister Sweeps Her House

This is a case of not getting what you expected.
I read the prologue and was charmed! It seemed a fairy tale-ish story about sisters (one who behaves, the other who doesn't) and a warning about a monster in a tunnel. Was this going to be a tale about whip-smart women facing down evil and coming out on top?
No, not at all.
There is so much violence in this book, and not much bothers me (I read a ton of horror), but this was so violent, including the first big act that sets off the chain that makes up this tale. Forget likeable, every one in this story is just in survivor mode: surviving poverty, surviving violent relationships, surviving an oppressive existence that is juxtaposed against an island paradise setting filled with privileged tourists.
Sadly, I couldn't really see who any of the characters were because their personalities and dreams are eclipsed by what happens to them. I found Wilma to be the most interesting character. Where was she finding the strength to carry on?
This is not an easy read. There is nothing charming about it. Like any good book, I'll probably be thinking about it for a long time. And there is a great deal to discuss here, I can see book clubs really chewing it up, if they can handle the violence.
Was it enjoyable to read? No. Is it an important book with a story that needs to be told? Possibly, if it is realistic. I'm concerned it leans toward poverty porn and being violent for the sake of being violent.