[Feldegast]

i tried again without quotes and got the same issue

then i tried copying the 2 files to the same directory and ran....
calibre-debug --diff 2.epub 1.epub
still got this error

Traceback (most recent call last):
File "site-packages/calibre/gui2/tweak_book/diff/main.py", line 458, in <lambda>
File "site-packages/calibre/gui2/tweak_book/diff/main.py", line 364, in file_diff
File "site-packages/calibre/gui2/tweak_book/diff/main.py", line 124, in file_diff
File "site-packages/calibre/gui2/tweak_book/diff/main.py", line 99, in get_decoded_raw
IOError: [Errno 2] No such file or directory: 'calibre-diff'



the purpose for providing the right click menu feature in the library is for those people who import book collections and end up with 5 or 6 copies of the same book where each copy is slightly different
being able to quickly compare 2 books to decide which to keep would save a lot of time

i would use the debug method but it looks like it is broken and for comparing lots of books less conveniant