Well, that's definitely stumping me, but let's hope someone can help!

It's weird the way the memory distorts things. With my 'ghost book', I had some vague memory of something important in it to do with a cat, but was sufficiently unsure about that bit to leave it out of my description when I asked about the book on the children's lit forum I found.

It turned out, of course, that the main character is called Cat.