[sleepy6553]

I've added books to my Calibre library in the past but I'm getting an error message today. I tried 2 different epub files but get the following error message. I added a book just a few days ago with no problem. Any suggestions? Thanks.

calibre, version 3.9.0
ERROR: Errors while adding: Failed to add any books, click "Show details" for more information


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Failed to add the book: The Handmaid's Tale
/var/folders/tq/4tcd6pln6r3d4410dr5rld240000gn/C/calibre_3.9.0_tmp_vl5IcU/90v0Jb_add_books/0/The Handmaids Tale.epub
With error:
Traceback (most recent call last):
File "site-packages/calibre/gui2/add.py", line 399, in add_book
File "site-packages/calibre/db/legacy.py", line 224, in create_book_entry
File "site-packages/calibre/db/cache.py", line 62, in call_func_with_lock
File "site-packages/calibre/db/cache.py", line 1552, in create_book_entry
File "site-packages/calibre/db/backend.py", line 843, in execute
File "src/cursor.c", line 236, in resetcursor
ReadOnlyError: ReadOnlyError: attempt to write a readonly database