[sumguy]

I'm considering switching from Sigil to Calibre's new book editor for making EPUBs from my PDF files. I use Mobipocket Creator to import a PDF file, it converts and saves as an HTML file and image files. Then I just copy that folder to my Mac. When I try to do "File->Import an HTML or DOCX file as a new book", and open the HTML file, I get this error:

calibre, version 1.26.0
ERROR: Failed to open book: Failed to open book, click Show details for more information.

Traceback (most recent call last):
File "site-packages/calibre/gui2/tweak_book/job.py", line 34, in run
File "site-packages/calibre/gui2/tweak_book/boss.py", line 183, in func
File "site-packages/calibre/ebooks/oeb/polish/import_book.py", line 50, in import_book_as_epub
File "site-packages/calibre/ebooks/oeb/polish/container.py", line 137, in __init__
InvalidBook: Could not locate opf file: u'/private/var/folders/m6/cngf28xj345f36n_kgc30_5c0000gn/T/calibre_1.26.0_tmp_WXgV2j/45oIm9eei/content.opf'

Not sure what I'm doing wrong, I'm not an ebook expert by any means... currently I just run Sigil, click the + button (add existing files) and select the HTML file. Everything gets imported, I do a bit of cleaning up, and save it as EPUB. So now I'm trying to see if I can do the same thing with Calibre's new editor, since I heard Sigil isn't being developed anymore. Ideas? Thanks...