@Override
 public synchronized void readUids(Book book) throws BookReadingException {
   readUidsNative(book);
   if (book.uids().isEmpty()) {
     book.addUid(BookUtil.createSHA256Uid(book.File));
   }
 }
 public String getBookHash() {
   final UID uid = BookUtil.createSHA256Uid(getReader().Model.Book.File);
   return uid != null ? uid.Id : null;
 }