Rated 5 out of 5 stars
Vast improvement! The standard address book is clumsy and barely adequate. The gContactSync extension helped but was also lacking. Cardbook is in a different league, with due allowance for the way vCard works. (It's good, not perfect.) For the first time in decades (no joke) I have all my contacts sorted and synchronised in one address book just a few days after installing Cardbook
BTW the review by Thecoalcracker that says there is no documentation is wrong. There is fairly thorough documentation via the GitHub developer's page.