I'm typing this because I own the novel, as well as the sequel and companion books. I type this up myself. I am also translating Codename Anastasia, so It will take long to upload every time~~~

All credit goes to Diana Wynne Jones >~< 

Also a bit of spoiler: The novel is very different than the movie, the movie was based on the novel, but it is somewhat different. It may come out confusing~!

This novel came out in 1986. The movie came out in 2004.