Multiplayer Book Copying
Solution 1:
The author of the book is set when you "sign" it, after that point it cannot be changed and creating a copy will give a book with identical author and contents to the original.
So the only way someone could change the author, would be to re-write the entire thing themselves or edit the files if they're the owner of the server. (This may also be possible with mods, but I don't know of any)