This story is dark. It is surreal, and often gruesome. The body count rivals that of your run-of-the-mill slasher film. In the very first chapter, two children get their heads cut off... in fact, there are several instances of people getting body parts cut off. People turn to stone or turn into animals. Almost every main character gets killed at least once (they get better, even the decapitations), and one of them actually goes to Hell (he gets back out). One character has an unsettling habit of jamming his whole arm down young girls' throats and yanking out their souls (the girls get better later). There is a dragon with an unsettling habit of tearing people to shreds (the people do NOT get better, but some of them get away). Did I mention that it's gruesome and surreal? It's a weird story, as the original Grimm's fairy tales are. Is it too much for children? I don't think so - I think children can tell the difference between a fantasy story and real life. 
 All that said, if the gore doesn't bother you (and most of it isn't as graphic as I've made it sound), the story has a lot of good stuff to say about family, the relationship between children and parents, and the potential children have within them to do great things even when they are little. It's an extended tale about Hansel and Gretel (and if you're worried about the gore, think about the classic Hansel and Gretel story - they cook the witch in her own oven at the end, remember? Did you ever have a problem with that as a child?) and both of them are characterized as children who are very independent and able to do amazing things, but they also spend the whole story in a search for parents who love them and will take care of them (those parents wind up being their own parents!) I can certainly see why people would consider this book controversial, but I think there's so much good to be said for it that there's no reason to be worried about sharing this book with a child who is old enough. I would be uncomfortable trying to read it out loud to my 4-year-old daughter, but I won't hesitate to share it with my 12-year-old son. If you are a parent, feel free to read through it yourself first to make sure your kids can understand it.