There are 900+ 'Empty Book' in my Library. That was the first real task I did with Calibre and my trusty (keyboard wedge) barcode scanner.
I used
Add from ISBN (right click the Add Books icon) for books that had ISBN codes. Do small batches (10-20) and resolve
any issues (bad cover, not found...) Add from ISBN also allows a 'Tag' to be includes in the entry (<in paper Library> was mine ) . It took me almost a year, doing a batch or 2 after work. Many had no ISBN (books from the 60's that needed Google and other help, Some needed my flat bed scanner

for the 'correct' cover.
You don't
need a barcode scanner to use Add from ISBN, but it does speed things up if you don't do 10key

.
IIRC Add from ISBN attempts to fetch covers and metadata from your configured sources. Have good Internet while doing.



Do this in a 'Intake' Library, Fix whatever needed, then
use '
Copy To Library' (delete): to
move to the Main Library. This allows corrections without contaminating the existing metadata with bad case.
Add Empty Book Starts with a form
(

do a group of books by Author +series in order. The one thing this does not allow is the Start of a Series numbering if a series is used. )