The style of writing was juvenile, not meant in a negative way at all. On the contrary, personally I would've devoured these books when I was in elementary school. Of course, I never did scare easily (I'd gone through the horror section of both the public library and video store before I hit double digits in age). The witches were scary, or would be with the correct audience. Witches who are bound to their bones so they are still a threat after death. Witches who aren't bound and are still a threat after death. Using children's blood in rituals, a few deaths, a truly haunted house. It would be too much for some children, and some adults for that matter. For me, it wasn't even creepy. It was interesting though, and overall, I enjoyed reading it.
It reminded me a lot of the old Grimm Fairy tales. Not the sanitized versions, the originals. I liked the storyline and plot, and I may one day read another in the series. I'm just not overly eager to do it anytime soon. I just don't think I'm the target audience any longer.
This book reminds me of a quote by C. S. Lewis, "A children's story that can only be enjoyed by children is not a good children's story in the slightest." It's a good story and can be enjoyed by people of all ages.