Rated 5 out of 5 stars

le Thecoalcracker ar Feabh. 18, 2021 ·

Great addon until ver 55.5. All address books disappeared. Restored Thunderbird. Installed ver 55.6 with same nasty results. Again, restored Tbird. Last working version is 55.2.

Update: Restarting Tbird did the trick. Thanks for the quick response.

Léirmheas ar leagan níos sine den bhreiseán seo (55.6). 

le Philippe V. (Forbróir) ar Feabh. 18, 2021 ·

workaround here : https://gitlab.com/CardBook/CardBook/-/issues/1172#note_512218318

Rated 4 out of 5 stars

le Thecoalcracker ar Ean. 2, 2021 ·

No user documentation. TB and Cardbook contacts don't agree. Not very usable in its' current (outdated contacts) state. Wish I could start from scratch and go from there.
And I don't care about any syncronization. Perhaps not use this add-on?
Update (after much investigating):
1. Deleted all address books in Cardbook.
2. Cardbook>hamburger>add new address book. And there it was: Import Thunderbird's standard address books.

Other than my initial mass confusion, Cardbook appears to be very usable.

Léirmheas ar leagan níos sine den bhreiseán seo (54.9). 

le Philippe V. (Forbróir) ar Ean. 2, 2021 ·

documentation here : https://gitlab.com/CardBook/CardBook/-/wikis/Documentation