There are just a few authors that my 12 year old and I trust implicitly.
After having raced through umpteen of her novels, we placed Diana Wynne Jones in that category. Sure, The Magicians of Caprona was kind of stupid.... But if you locked us in a library, with a short deadline in which to emerge with a book we were willing to read, it might very well be one by Diana Wynne Jones.
Fire and Hemlock is quite a bit different from other Jones' novels. For one thing, it is SPOOKY. It is, in fact, so intense, so spooky that if my daughter and I hadn't trusted Jones as much as we did, we would never have finished reading this story.
On the other hand, many of the characters do resemble other Jones characters we've met in her other stories. For one thing, every young woman of child-bearing age is at the very least utterly self-involved and uncaring about her children.