I'm writing a mystery novel for children. So, there is this part, where a book is stolen( from a personal library), but its not stolen because its rare. But I can't find any reason for someone to steal a book other than for selling it. So, I was wondering if someone could help me find reasons, for a book to be stolen. Like, I thought that a good reason could be that there was some important document in the book,that could make the antagonist to steal the book. But I realised that , if that was the case, the thief need only take the document and not the whole book.