Use random UUIDs as book id

src/libprs500/ebooks/lrf/__init__.py

@@ -19,6 +19,7 @@ The LRF file format is documented at U{http://www.sven.de/librie/Librie/LrfForma
 import sys, os
 from optparse import OptionParser, OptionValueError
 from htmlentitydefs import name2codepoint
+from uuid import uuid4
 
 from ttfquery import describe, findsystem
 from fontTools.ttLib import TTLibError
@@ -283,6 +284,7 @@ def Book(options, logger, font_delta=0, header=None,
     book = _Book(textstyledefault=tsd, 
                 pagestyledefault=ps, 
                 blockstyledefault=dict(blockwidth=ps['textwidth']),
+                bookid=uuid4().hex,
                 **settings)
     for family in fonts.keys():
         if fonts[family]: