Hmm, infuriating
I have 4 books, all giving the same error message, or a variation thereof. I've re-downloaded python and the other bits but the errors, on both windows machines are the same so I'm doing something dumb somewhere.
I assume you don't have to create or put the books in any special folder (as the programme asks you for the directory) and I assume you can call the output file any name you wish ie test.epub, though I've tried numerous combinations.
regards, Howard