Sophie I think that whether this book is appropriate for your niece depends more on how mature she is. I read this book when I was 13, and I thought it was pretty scary, but I was able to handle it. I think that it might be a bit to big of a book for a 12 year old, but older than that should be fine. The only problem with younger may be that they might not enjoy the writing as they may find it too complicated. It is lovely writing though.